Method and apparatus for allocating control channel candidates

ABSTRACT

A method and an apparatus for allocating control channel candidates is provided, which can allocate control channel candidates at different aggregation levels to K ePDCCH sets and reduce complexity of blind detection performed by a UE. The method includes: determining K sets for transmitting a control channel, where each set in the K sets includes at least one physical resource block pair; and allocating control channel candidates at each aggregation level to at least one set in the K sets according to at least one of aggregation levels supported by the control channel to be transmitted, the number of control channel candidates corresponding to each aggregation level, the K sets for transmitting the control channel, and types of the sets.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/668,506, filed on Mar. 25, 2015, which is a continuation ofInternational Application No. PCT/CN2012/082217, filed on Sep. 27, 2012.All of the afore-mentioned patent applications are hereby incorporatedby reference in their entireties.

TECHNICAL FIELD

The present application relates to the communications field, and inparticular, to a method and an apparatus for allocating control channelcandidates.

BACKGROUND

In an LTE (long term evolution) Rel-8/9/10 communication system, adynamic scheduling technology is used to improve performance of thesystem. In other words, an eNB (evolved Node Base, evolved base station)schedules and allocates resources according to channel conditions ofeach UE (user equipment), so that each scheduled UE performstransmission on an optimal channel of the UE. In downlink transmission,the eNB sends a PDSCH (physical downlink shared channel) and acorresponding PDCCH (physical downlink control channel) to eachscheduled UE according to a dynamic scheduling result, where the PDSCHcarries data sent by the eNB to the scheduled UE, and the PDCCH ismainly used to indicate a transport format of the corresponding PDSCH,including scheduling information such as resource allocation, transportblock size, modulation and coding scheme, transport rank, and precodingmatrix information.

In a subframe, each PDCCH used for downlink and uplink scheduling ismultiplexed in N (N>1) CCEs numbered n=0, 1, . . . , N−1 in a PDCCHregion. Each PDCCH has 4 aggregation levels in total, namely, 1, 2, 4,and 8, which means, the PDCCH may be formed by aggregation of 1, 2, 4,or 8 consecutive CCEs. The aggregation level corresponding to each PDCCHis determined by the size of information blocks in the PDCCH and achannel of a UE corresponding to the PDCCH. Information in each PDCCH ismapped through the N CCEs to REs reserved for the PDCCH and is sent to aUE.

At a receiving end, the UE needs to blindly detect the N CCEs to obtaina PDCCH needed by the UE. The number of PDCCH candidates at eachaggregation level is limited. A smaller number of PDCCH candidatesindicate a smaller number of times of blind detections. For example,when aggregation level 1 is 8, there are only two PDCCH candidates,which means, CCEs 0 to 7 and CCEs 8 to 15 are detected. Although thisPDCCH candidate allocation principle can reduce the number of times ofblind detections, the number of times of blind detections needed at eachaggregation level is still approximately in direct proportion to thenumber N of CCEs in the PDCCH region. To further reduce complexity ofblind detections, the maximum number of PDCCH candidates to be blindlydetected, namely, a search space, is limited at each aggregation level.The search space is classified into a common search space and aUE-specific search space. The difference between the two search spaceslies in that a start CCE of the common search space is in a fixedposition, while a start CCE of the UE-specific search space isdetermined by a UE identity and a subframe number of a PDCCH, where thecommon search space and the UE-specific search space may overlap. Afterthe number of PDCCH candidates included in the search space is set, theUE may start to perform a specified number of times of blind detectionsfrom the start CCE according to an aggregation level supported by thePDCCH candidates, thereby reducing the complexity of blind detections.For example, the number of CCEs in a PDCCH region is N=18, a start CCEof a UE-specific search space is 0, and the numbers of PDCCH candidatesat aggregation levels 1=1, 2, 4, and 8 are 6, 6, 2, and 2 respectively;then, when 1=1, there are 6 PDCCH candidates, and there is oneaggregated CCE in each PDCCH, and therefore, the UE needs to performonly 6 blind detections for 6 consecutive CCEs starting from the startCCE; when 1=4, there are 2 PDCCH candidates, and there are 4 aggregatedCCEs in each PDCCH, and therefore, the UE needs to perform only 2 blinddetections for 2*4=8 consecutive CCEs starting from the start CCE.

In LTE Rel-11, an existing PDCCH is enhanced, in other words, a part ofresources are divided from an original PDSCH region to transmit anenhanced PDCCH to form an ePDCCH (enhanced physical downlink controlchannel), so that capacity of the PDCCH and the number of simultaneouslyscheduled UEs are increased. The ePDCCH may be formed by aggregation ofone or more eCCEs (enhanced control channel elements), and anaggregation level may be obtained according to CSI feedback information.According to whether the ePDCCH is transmitted in consecutivetime-frequency resource positions, in other words, whether an eCCE islocated in one physical resource block pair (corresponding to alocalized transmission mode) or located in multiple distributed physicalresource block pairs (corresponding to a distributed transmission mode),a transmission mode of the ePDCCH may be classified into a localizedmode and a distributed mode.

Given a Normal subframe and a Normal CP or special subframeconfigurations 3, 4, and 8 (Normal CP), when the number of validresource elements in each PRB Pair is less than a threshold, aggregationlevels used by the localized transmission mode are 2, 4, 8, and 16, andaggregation levels used by the distributed transmission mode are 2, 4,8, 16, and 32. In all other cases, aggregation levels used by thelocalized transmission mode are 1, 2, 4, and 8, and aggregation levelsused by the distributed transmission mode are 1, 2, 4, 8, and 16. In asubframe, the UE may simultaneously detect control channel candidates ofthe localized transmission mode and distributed transmission mode. Atthe 3GPP RAN1#70, a conclusion on the design of a search space for anePDCCH mainly includes: configuring K sets for a search space, whereeach set is made up of N PRB pairs, where N is equal to one of 1, 2, 4,8, and 16, and the PRB pairs in each set may completely overlap orpartially overlap. The maximum value of K is one of {2, 3, 4, 6}, wherethere are K_(L) localized sets and K_(D) distributed sets (K_(L) andK_(D) may be equal to 0), and the total number of times of blinddetections is 32 or 48 and does not change according to the value of K.

When the UE performs blind detections for the search space of the Ksets, the total number of times of blind detections is fixed. To reducethe complexity of blind detections, some limitations to the number ofcontrol channel candidates allocated in the K ePDCCH sets need to bemade for each aggregation level; however, the prior art does not providea method for allocating control channel candidates.

SUMMARY

Embodiments of the present application provide a method and an apparatusfor allocating control channel candidates, which can allocate controlchannel candidates at different aggregation levels to K ePDCCH sets andreduce complexity of blind detections performed by a UE.

To achieve the foregoing objectives, the embodiments of the presentapplication adopt the following technical solutions:

According to a first aspect, a method for allocating control channelcandidates is provided and includes:

determining K sets for transmitting a control channel, where each set inthe K sets includes at least one physical resource block pair, and K isa positive integer greater than 0; and

allocating each control channel candidate to at least one set in the Ksets according to at least one of aggregation levels supported by thecontrol channel, the number of control channel candidates correspondingto each aggregation level, the K sets for transmitting the controlchannel, and types of the sets.

In a first possible implementation manner, the K sets for transmittingthe control channel include a set of a localized transmission mode and aset of a distributed transmission mode, where the number of sets of thelocalized transmission mode is K_(L), and the number of sets of thedistributed transmission mode is K_(D), K_(L)+K_(D)=K, and K_(L) andK_(D) are integers greater than or equal to 0; and

the aggregation levels supported by the control channel include one ormore of the following levels:

aggregation levels supported by the localized transmission mode,aggregation levels supported by the distributed transmission mode, andcommon aggregation levels supported by both the localized transmissionmode and the distributed transmission mode.

In a second possible implementation manner, with reference to the firstpossible implementation manner of the first aspect, the allocatingcontrol channel candidates at each aggregation level to at least one setin the K sets according to the aggregation levels supported by thecontrol channel to be transmitted, the number of control channelcandidates corresponding to each aggregation level and determinedaccording to a preset rule, the K sets for transmitting the controlchannel, and the types of the sets, includes:

when K_(L) is a positive integer, allocating all control channelcandidates at the aggregation levels supported by the localizedtransmission mode to at least one of the K_(L) sets; or

when K_(D) is a positive integer, allocating all control channelcandidates at the aggregation levels supported by the distributedtransmission mode to at least one of the K_(D) sets; or

when both K_(L) and K_(D) are positive integers, allocating all controlchannel candidates at each aggregation level in the aggregation levelssupported by both the localized transmission mode and the distributedtransmission mode to at least one of the K_(D) sets and at least one ofthe K_(L) sets.

In a third possible implementation manner, both K_(L) and K_(D) arepositive integers, all control channel candidates at each aggregationlevel in the aggregation levels supported by both the localizedtransmission mode and the distributed transmission mode are allocated toat least one of the K_(D) sets and at least one of the K_(L) sets,

at least one half of all control channel candidates at each firstaggregation level in the aggregation levels supported by both thelocalized transmission mode and the distributed transmission mode areallocated to at least one of the K_(L) sets; and

at least one half of all control channel candidates at each secondaggregation level in the aggregation levels supported by both thelocalized transmission mode and the distributed transmission mode areallocated to at least one of the K_(D) sets.

In a fourth possible implementation manner, the allocating all controlchannel candidates at an aggregation level supported by only thedistributed transmission mode or the localized transmission mode to atleast one set in the K_(D) sets of the distributed transmission mode orin the K_(L) sets of the localized transmission mode, includes:

determining, according to the number of sets used for the aggregationlevel in K_(D) or K_(L), the number of control channel candidatesallocated to each set in the K_(D) or K_(L) sets, at the aggregationlevel; or

determining, according to a ratio of the number of physical resourceblocks of each set in sets used for the aggregation level in K_(D) orK_(L), the number of control channel candidates allocated to each set inthe K_(D) or K_(L) sets, at the aggregation level.

In a fifth possible implementation manner, both K_(L) and K_(D) arepositive integers, all control channel candidates at each aggregationlevel in the aggregation levels supported by both the localizedtransmission mode and the distributed transmission mode are allocated toat least one of the K_(D) sets and at least one of the K_(L) sets,

according to a ratio between the numbers of sets used for theaggregation level in K_(D) and K_(L), the numbers of control channelcandidates allocated to the K_(L) and K_(D) sets are determined, at eachaggregation level; or

according to a ratio between the total numbers of physical resourceblocks in sets used for the aggregation level in K_(D) and K_(L), thenumbers of control channel candidates allocated to the K_(L) and K_(D)sets are determined, at each aggregation level; or

according to a ratio of the number of physical resource blocks of eachset in sets used for the aggregation level in K_(D) and K_(L), thenumber of control channel candidates allocated to each set in the K_(L)and K_(D) sets is determined, at each aggregation level.

Optionally, at each aggregation level, when the number of controlchannel candidates configured for the K_(L) (greater than 1) sets isgreater than 1, the number of control channel candidates in each set isdetermined according to the number of physical resource blocks includedin each set that can support the aggregation level in the K_(L) sets orthe number of sets that can support the aggregation level in the K_(L)sets, or

when the number of control channel candidates configured for the K_(D)(greater than 1) sets is greater than 1, the number of control channelcandidates in each set is determined according to the number of physicalresource blocks included in each set that can support the aggregationlevel in the K_(D) sets or the number of sets that can support theaggregation level in the K_(D) sets.

Optionally, at each aggregation level supported by the control channelto be transmitted, the number of control channel candidates allocated tothe K_(L) sets of the localized transmission mode and the number ofcontrol channel candidates allocated to the K_(D) sets of thedistributed transmission mode are functions of at least one of thenumber of control channel candidates at the aggregation level, thenumber K_(L) of sets of the localized transmission mode, and the numberK_(D) of sets of the distributed transmission mode.

Optionally, when the number of control channel candidates correspondingto the aggregation levels supported by both the localized transmissionmode and the distributed transmission mode is an even number, the numberof control channel candidates allocated to the K_(L) sets of thelocalized transmission mode meets the following formula:

${{M^{(L)}/2} + \left\lfloor {\frac{K_{L}}{K_{L} + K_{D}} \cdot {M^{(L)}/2}} \right\rfloor};$and the number of control channel candidates allocated to the K_(D) setsof the distributed transmission mode meets the following formula:

${{M^{(L)}/2} - \left\lfloor {\frac{K_{L}}{K_{L} + K_{D}} \cdot {M^{(L)}/2}} \right\rfloor};$

when the number of control channel candidates corresponding to the loweraggregation levels is an odd number, the number of control channelcandidates allocated to the K_(L) sets of the localized transmissionmode meets the following formula:

${{\left( {M^{(L)} + 1} \right)/2} + \left\lfloor {\frac{K_{L}}{K_{L} + K_{D}} \cdot {\left( {M^{(L)} - 1} \right)/2}} \right\rfloor};$and the number of control channel candidates allocated to the K_(D) setsof the distributed transmission mode meets the following formula:

${{\left( {M^{(L)} - 1} \right)/2} - \left\lfloor {\frac{K_{L}}{K_{L} + K_{D}} \cdot {\left( {M^{(L)} - 1} \right)/2}} \right\rfloor};$and

an allocation ratio of all candidates at aggregation levels where thenumber of control channel candidates is 2, is 1:1 between the K_(L) setsof the localized transmission mode and the K_(D) sets of the distributedtransmission mode.

Optionally, at least one set in the determined K sets for transmittingthe control channel is used to allocate control channel candidates atone or two aggregation levels.

A rule for determining aggregation levels that can be supported by thecontrol channel to be transmitted includes:

when the total number of aggregation levels that can be supported by thecontrol channel is N, obtaining, according to the number of validphysical resource elements included in each physical resource blockpair, k (k<=N) aggregation levels in the N aggregation levels asaggregation levels of the control channel to be transmitted, or

configuring, semi-statically through RRC signaling, k (k<=N) aggregationlevels in the N aggregation levels as aggregation levels that can besupported by the control channel to be transmitted.

A form of semi-static configuration through RRC signaling is a bitmap.

If the number of aggregation levels of the control channel to betransmitted is N, the numbers of control channel candidatescorresponding to any p (p<=4) aggregation levels in 4 aggregation levels(1, 2, 4, 8) in an original protocol are respectively configured forcorresponding aggregation levels in the N aggregation levels of thecontrol channel to be transmitted, and the numbers of control channelcandidates corresponding to remaining (4-p) aggregation levels in the 4aggregation levels (1, 2, 4, 8) in the original protocol arecorrespondingly configured for remaining N-p aggregation levels in the Naggregation levels of the control channel to be transmitted.

When the aggregation levels supported by the control channel to betransmitted include 32, and the number of available resource elements ineach physical resource block pair except resource elements of othersignals, such as a CRS, a DMRS, a CSI-RS, a PDCCH, is greater than orequal to 72, a user terminal does not detect control channel candidatesat aggregation level 32; otherwise, the user terminal detects thecontrol channel candidates at aggregation level 32;

or, when the aggregation levels supported by the control channel to betransmitted do not include 32, and the number of available resourceelements in each physical resource block pair except resource elementsof other signals, such as a CRS, a DMRS, a CSI-RS, a PDCCH, is less than72, a user terminal detects control channel candidates at aggregationlevel 8.

When the control channel to be transmitted is transmitted with anextended cyclic prefix, and the supported aggregation levels include 16,and the number of available resource elements in each physical resourceblock pair except resource elements of other signals, such as a CRS, aDMRS, a CSI-RS, a PDCCH, is greater than or equal to 72, a user terminaldoes not detect control channel candidates at aggregation level 16;otherwise, the user terminal detects the control channel candidates ataggregation level 16;

or, when the control channel to be transmitted is transmitted with anextended cyclic prefix, and the supported aggregation levels do notinclude 16, and the number of available resource elements in eachphysical resource block pair except resource elements of other signals,such as a CRS, a DMRS, a CSI-RS, a PDCCH, is less than 72, a userterminal detects PDCCH candidates at aggregation level 8.

The K_(L) and K_(D) for transmitting the control channel are configured,and the number of physical resource block pairs included in each set isconfigured; or the K_(L) and K_(D) for transmitting the control channelare fixed, the number of physical resource block pairs included in eachset is configured, and allocation of all control channel candidates ateach aggregation level to the K_(L) and K_(D) sets is fixed.

In a second aspect, an apparatus for allocating control channelcandidates is provided and includes:

a determining unit, configured to determine K sets for transmitting acontrol channel, where each set in the K sets includes at least onephysical resource block pair, and K is a positive integer greater than0; and

an allocating unit, configured to allocate, according to at least one ofaggregation levels supported by the control channel, the number ofcontrol channel candidates corresponding to each aggregation level, theK sets for transmitting the control channel, and types of the sets, eachcontrol channel candidate to at least one set in the K sets determinedby the determining unit.

In a first possible implementation manner, the K sets for transmittingthe control channel include a set of a localized transmission mode and aset of a distributed transmission mode, where the number of sets of thelocalized transmission mode is K_(L), and the number of sets of thedistributed transmission mode is K_(D), K_(L)+K_(D)=K, and K_(L) andK_(D) are integers greater than or equal to 0; and

the aggregation levels supported by the control channel include one ormore of the following levels:

aggregation levels supported by the localized transmission mode,aggregation levels supported by the distributed transmission mode, andcommon aggregation levels supported by both the localized transmissionmode and the distributed transmission mode.

The allocating unit is specifically configured to: when K_(L) is apositive integer, allocate all control channel candidates at theaggregation levels supported by the localized transmission mode to atleast one of the K_(L) sets; or when K_(D) is a positive integer,allocate all control channel candidates at the aggregation levelssupported by the distributed transmission mode to at least one of theK_(D) sets; or when both K_(L) and K_(D) are positive integers, allocateall control channel candidates at each aggregation level in theaggregation levels supported by both the localized transmission mode andthe distributed transmission mode to at least one of the K_(D) sets andat least one of the K_(L) sets.

Optionally, the allocating unit being configured to allocate all controlchannel candidates at each aggregation level in the aggregation levelssupported by both the localized transmission mode and the distributedtransmission mode to at least one of the K_(D) sets and at least one ofthe K_(L) sets when both K_(L) and K_(D) are positive integers,includes:

allocating at least one half of all control channel candidates at eachfirst aggregation level in the aggregation levels supported by both thelocalized transmission mode and the distributed transmission mode to atleast one of the K_(L) sets; and allocating at least one half of allcontrol channel candidates at each second aggregation level in theaggregation levels supported by both the localized transmission mode andthe distributed transmission mode to at least one of the K_(D) sets.

Optionally, when the number of control channel candidates at theaggregation level is 2, remaining control channel candidates are notplaced in any set corresponding to a transmission mode of a firstcontrol channel candidate.

Optionally, the allocating unit being configured to allocate all controlchannel candidates at an aggregation level supported by only thedistributed transmission mode or the localized transmission mode to atleast one set in the K_(D) sets of the distributed transmission mode orin the K_(L) sets of the localized transmission mode, includes:

determining, according to the number of sets used for the aggregationlevel in K_(D) or K_(L), the number of control channel candidatesallocated to each set in the K_(D) or K_(L) sets, at the aggregationlevel; or

determining, according to a ratio of the number of physical resourceblocks of each set in sets used for the aggregation level in K_(D) orK_(L), the number of control channel candidates allocated to each set inthe K_(D) or K_(L) sets, at the aggregation level.

Optionally, the allocating unit being configured to allocate all controlchannel candidates at each aggregation level in the aggregation levelssupported by both the localized transmission mode and the distributedtransmission mode to at least one of the K_(D) sets and at least one ofthe K_(L) sets when both K_(L) and K_(D) are positive integers,includes:

determining, according to a ratio between the numbers of sets used forthe aggregation level in K_(D) and K_(L), the numbers of control channelcandidates allocated to the K_(L) and K_(D) sets, at each aggregationlevel; or

determining, according to a ratio between the total numbers of physicalresource blocks in sets used for the aggregation level in K_(D) andK_(L), the numbers of control channel candidates allocated to the K_(L)and K_(D) sets, at each aggregation level; or

determining, according to a ratio of the number of physical resourceblocks of each set in sets used for the aggregation level in K_(D) andK_(L), the number of control channel candidates allocated to each set inthe K_(L) and K_(D) sets, at each aggregation level.

Optionally, at each aggregation level, the numbers of control channelcandidates allocated to the K_(L) and K_(D) sets are configured. Theconfiguration is a higher-layer semi-static configuration.

At each aggregation level, when the number of control channel candidatesconfigured for the K_(L) (greater than 1) sets is greater than 1, theallocating unit is configured to determine the number of control channelcandidates in each set according to the number of physical resourceblocks included in each set that can support the aggregation level inthe K_(L) sets or the number of sets that can support the aggregationlevel in the K_(L) sets, or

when the number of control channel candidates configured for the K_(D)(greater than 1) sets is greater than 1, the allocating unit isconfigured to determine the number of control channel candidates in eachset according to the number of physical resource blocks included in eachset that can support the aggregation level in the K_(D) sets or thenumber of sets that can support the aggregation level in the K_(D) sets.

At each aggregation level supported by the control channel to betransmitted, the number of control channel candidates allocated to theK_(L) sets of the localized transmission mode and the number of controlchannel candidates allocated to the K_(D) sets of the distributedtransmission mode are functions of at least one of the number of controlchannel candidates at the aggregation level, the number K_(L) of sets ofthe localized transmission mode, and the number K_(D) of sets of thedistributed transmission mode.

When the number of control channel candidates corresponding to theaggregation levels supported by both the localized transmission mode andthe distributed transmission mode is an even number, the number ofcontrol channel candidates allocated to the K_(L) sets of the localizedtransmission mode meets the following formula:

${{M^{(L)}/2} + \left\lfloor {\frac{K_{L}}{K_{L} + K_{D}} \cdot {M^{(L)}/2}} \right\rfloor};$and the number of control channel candidates allocated to the K_(D) setsof the distributed transmission mode meets the following formula:

${{M^{(L)}/2} - \left\lfloor {\frac{K_{L}}{K_{L} + K_{D}} \cdot {M^{(L)}/2}} \right\rfloor};$

when the number of control channel candidates corresponding to the loweraggregation levels is an odd number, the number of control channelcandidates allocated to the K_(L) sets of the localized transmissionmode meets the following formula:

${{\left( {M^{(L)} + 1} \right)/2} + \left\lfloor {\frac{K_{L}}{K_{L} + K_{D}} \cdot {\left( {M^{(L)} - 1} \right)/2}} \right\rfloor};$and the number of control channel candidates allocated to the K_(D) setsof the distributed transmission mode meets the following formula:

${{\left( {M^{(L)} - 1} \right)\text{/}2} - \left\lfloor {{\frac{K_{L}}{K_{L} + K_{D}} \cdot \left( {M^{(L)} - 1} \right)}\text{/}2} \right\rfloor};$and

an allocation ratio of all candidates at aggregation levels where thenumber of control channel candidates is 2, is 1:1 between the K_(L) setsof the localized transmission mode and the K_(D) sets of the distributedtransmission mode.

Optionally, the allocating unit is configured to determine that at leastone set in the K sets for transmitting the control channel is used toallocate control channel candidates at one or two aggregation levels.

Optionally, a rule for determining aggregation levels that can besupported by the control channel to be transmitted includes:

when the total number of aggregation levels that can be supported by thecontrol channel is N, obtaining, according to the number of validphysical resource elements included in each physical resource blockpair, k (k<=N) aggregation levels in the N aggregation levels asaggregation levels of the control channel to be transmitted, or

configuring, semi-statically through RRC signaling, k (k<=N) aggregationlevels in the N aggregation levels as aggregation levels that can besupported by the control channel to be transmitted.

A form of semi-static configuration through RRC signaling is a bitmap.

If the number of aggregation levels of the control channel to betransmitted is N, the numbers of control channel candidatescorresponding to any p (p<=4) aggregation levels in 4 aggregation levels(1, 2, 4, 8) in an original protocol are respectively configured forcorresponding aggregation levels in the N aggregation levels of thecontrol channel to be transmitted, and the numbers of control channelcandidates corresponding to remaining (4-p) aggregation levels in the 4aggregation levels (1, 2, 4, 8) in the original protocol arecorrespondingly configured for remaining N-p aggregation levels in the Naggregation levels of the control channel to be transmitted.

Optionally, the apparatus further includes a detecting unit, where: whenthe aggregation levels supported by the control channel to betransmitted include 32, and the number of available resource elements ineach physical resource block pair except resource elements of othersignals, such as a CRS, a DMRS, a CSI-RS, a PDCCH, is greater than orequal to 72, the detecting unit does not detect control channelcandidates at aggregation level 32; otherwise, the detecting unitdetects the control channel candidates at aggregation level 32; or, whenthe aggregation levels supported by the control channel to betransmitted do not include 32, and the number of available resourceelements in each physical resource block pair except resource elementsof other signals, such as a CRS, a DMRS, a CSI-RS, a PDCCH, is less than72, the detecting unit detects control channel candidates at aggregationlevel 8.

Optionally, when the control channel to be transmitted is transmittedwith an extended cyclic prefix, and the supported aggregation levelsinclude 16, and the number of available resource elements in eachphysical resource block pair except resource elements of other signals,such as a CRS, a DMRS, a CSI-RS, a PDCCH, is greater than or equal to72, the detecting unit does not detect control channel candidates ataggregation level 16; otherwise, the detecting unit detects the controlchannel candidates at aggregation level 16; or, when the control channelto be transmitted is transmitted with an extended cyclic prefix, and thesupported aggregation levels do not include 16, and the number ofavailable resource elements in each physical resource block pair exceptresource elements of other signals, such as a CRS, a DMRS, a CSI-RS, aPDCCH, is less than 72, the detecting unit detects PDCCH candidates ataggregation level 8.

Optionally, the K_(L) and K_(D) for transmitting the control channel areconfigured, and the number of physical resource block pairs included ineach set is configured; or the K_(L) and K_(D) for transmitting thecontrol channel are fixed, the number of physical resource block pairsincluded in each set is configured, and allocation of all controlchannel candidates at each aggregation level to the K_(L) and K_(D) setsis fixed.

In a third aspect, an apparatus for allocating control channelcandidates is provided and includes: a receiver, a transmitter, amemory, and a processor that is connected to the receiver, thetransmitter, and the memory, where the memory stores a group of programcodes, and the processor invokes the program codes in the memory toperform the method provided by the first aspect.

In the method and apparatus for allocating control channel candidatesaccording to the above technical solutions, K sets for transmitting acontrol channel are determined, and control channel candidates at eachaggregation level are allocated to at least one set in the K setsaccording to at least one of aggregation levels supported by the controlchannel to be transmitted, the number of control channel candidatescorresponding to each aggregation level, the K sets for transmitting thecontrol channel, and types of the sets. Therefore, control channelcandidates at different aggregation levels can be allocated to K ePDCCHsets, and a search space of a UE is defined, thereby reducing complexityof blind detection performed by the UE.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the presentapplication more clearly, the following briefly introduces theaccompanying drawings required for describing the embodiments.Apparently, the accompanying drawings in the following description showmerely some embodiments of the present application, and a person ofordinary skill in the art may still derive other drawings from theseaccompanying drawings without creative efforts.

FIG. 1 is a schematic flowchart of a method for allocating controlchannel candidates according to an embodiment of the presentapplication;

FIG. 2 is a structural block diagram of an apparatus for allocatingcontrol channel candidates according to an embodiment of the presentapplication; and

FIG. 3 is a structural block diagram of another apparatus for allocatingcontrol channel candidates according to an embodiment of the presentapplication.

DETAILED DESCRIPTION

The following clearly describes the technical solutions in theembodiments of the present application with reference to theaccompanying drawings in the embodiments of the present application.Apparently, the described embodiments are merely a part rather than allof the embodiments of the present application. All other embodimentsobtained by a person of ordinary skill in the art based on theembodiments of the present application without creative efforts shallfall within the protection scope of the present application.

An embodiment of the present application provides a method forallocating control channel candidates (EPDCCH candidates). As shown inFIG. 1, the method includes the following:

101. Determine K sets for transmitting a control channel, where each setin the K sets includes at least one physical resource block pair, and Kis a positive integer greater than 0.

There are two transmission modes for an ePDCCH, namely, localizedtransmission and distributed transmission. The localized transmissionmeans that each eCCE aggregated into the ePDCCH is mapped to a PRB pair,and the distributed transmission means that each eCCE aggregated intothe ePDCCH may be mapped to several non-consecutive PRB pairs in thefrequency domain.

For a UE, ePDCCH resources used for the localized transmission anddistributed transmission are configured by an eNB. This configurationmay be dynamic or semi-static allocation. For ease of description,without loss of generality, in the embodiment of the presentapplication, configurations of resources are described by using sets,and ePDCCH resources allocated by the eNB to the UE may be configured asK sets, where K is an integer greater than 0. Therefore, the set is alsoreferred to as a resource set or an ePDCCH set. The K sets include twotypes: a set of a localized transmission mode and a set of a distributedtransmission mode. The K sets for transmitting the control channelinclude K_(L) sets of the localized transmission mode and K_(D) sets ofthe distributed transmission mode, where K_(L)+K_(D)=K, and K_(L) andK_(D) are integers greater than or equal to 0.

Each set includes N (N>=1) PRB pairs. When ePDCCH resources areconfigured, according to values of K_(L) and K_(D), there may be thefollowing cases: K=K_(L), and K_(D)=0, which means, the eNB allocatesonly K_(L)>=1 sets of the localized transmission mode to the UE;K=K_(D), and K_(L)=0, which means, the eNB allocates only K_(D)>=1 setsof the distributed transmission mode to the UE; K=K_(L)+K_(D), whereboth K_(L) and K_(D) are not 0, which means, the eNB simultaneouslyallocates K_(L)>=1 sets of the localized transmission mode and K_(D)>=1sets of the distributed transmission mode to the UE, where the number ofPRB pairs in different sets may be the same or different, which is notlimited by the embodiment of the present application.

When control channel candidates are allocated to the K sets (the controlchannel candidates may also be referred to as candidates), values of K,K_(L), and K_(D) need to be determined first. The K_(L) and K_(D) fortransmitting the control channel are configured, and the number ofphysical resource block pairs included in each set is configured; or theK_(L) and K_(D) for transmitting the control channel are fixed, thenumber of physical resource block pairs included in each set isconfigured, and allocation of all control channel candidates at eachaggregation level to the K_(L) and K_(D) sets is fixed.

Herein the configuration refers to parameters configured by the basestation for the UE through higher-layer signaling, which means, valuesof the K_(L) and K_(D) and the number of physical resource block pairsincluded in each set may all be configured by the base station for theUE.

102. Allocate control channel candidates at each aggregation level to atleast one set in the K sets according to at least one of aggregationlevels supported by the control channel to be transmitted, the number ofcontrol channel candidates corresponding to each aggregation level, theK sets for transmitting the control channel, and types of the sets.

To facilitate blind detections performed by the UE, an ePDCCH searchspace needs to be defined in all the configured K ePDCCH sets. Forexample, ePDCCH sets configured for a UE include a set of the localizedtransmission mode and a set of the distributed transmission mode, andthe number of PRB pairs in the configured set of the localizedtransmission mode is 8 and the number of PRB pairs in the configured setof the distributed transmission mode is 4, and 4 eCCEs may betransmitted in each PRB pair. Therefore, the set of the localizedtransmission mode and the set of the distributed transmission modeinclude 32 eCCEs and 16 eCCEs respectively, 48 eCCEs in total. TheePDCCH search space of the UE needs to be defined on the 48 eCCEs.Specifically, on the 48 eCCEs, eCCE positions of the control channelcandidates at different aggregation levels are determined, in the otherwords, the number and eCCE positions of control channel candidates atdifferent aggregation levels in the set of the localized transmissionmode and the set of the distributed transmission mode are determined.

For the localized transmission mode and distributed transmission mode,generally when the base station can obtain accurate CSI feedback of atransmission channel of the UE, the base station can obtain a frequencyscheduling gain and a beamforming gain by using the localizedtransmission mode. Therefore, a lower aggregation level may be used foran ePDCCH, for example, aggregation levels 1 and 2 can satisfyperformance requirements. Otherwise, when the base station cannot obtainaccurate or timely CSI feedback, the base station cannot obtain thefrequency scheduling gain and beamforming gain. To ensure transmissionperformance of the ePDCCH, the distributed transmission mode needs to beused. Therefore, generally a higher aggregation level is used fortransmission, for example, aggregation level 8, 16, or 32. Therefore, inthe embodiment of the present application, in common aggregation levelssupported by both the localized transmission mode and the distributedtransmission mode, at least one half of candidates at a loweraggregation level are placed in the region of the set of the localizedtransmission mode, and at least one half of candidates at a higheraggregation level are placed in the region of the set of the distributedtransmission mode.

After obtaining the value of K configured by the eNB for the UE, the UEmay allocate the control channel candidates to at least one set in the Ksets. The allocation method may include the following three cases: Whenthe K_(L) is a positive integer, the UE may allocate all control channelcandidates at an aggregation level supported by only the localizedtransmission mode in the aggregation levels supported by the controlchannel to be transmitted to at least one set in the K_(L) sets of thelocalized transmission mode; and when the K_(D) is a positive integer,allocate all control channel candidates at an aggregation levelsupported by only the distributed transmission mode to at least one setin the K_(D) sets of the distributed transmission mode. When both theK_(L) and K_(D) are positive integers, all control channel candidates atthe aggregation levels supported by both the localized transmission modeand the distributed transmission mode are allocated to at least one ofthe K_(D) sets of the distributed transmission mode and at least one ofthe K_(L) sets of the localized transmission mode; and allocate allcontrol channel candidates at the aggregation level supported by onlythe distributed transmission mode or the localized transmission mode toat least one of the K_(D) sets of the distributed transmission mode orat least one of the K_(L) sets of the localized transmission mode.

The allocating all control channel candidates at the aggregation levelssupported by both the localized transmission mode and the distributedtransmission mode to at least one of the K_(D) sets of the distributedtransmission mode and at least one of the K_(L) sets of the localizedtransmission mode includes: allocating at least one half of all controlchannel candidates corresponding to a lower aggregation level in theaggregation levels supported by both the localized transmission mode andthe distributed transmission mode to at least one of the K_(L) sets ofthe localized transmission mode; and allocating at least one half of allcontrol channel candidates corresponding to a higher aggregation levelin the aggregation levels supported by both the localized transmissionmode and the distributed transmission mode to at least one of the K_(D)sets of the distributed transmission mode. As discussed at the 3GPPRAN1#70, for ePDCCH, given a Normal subframe and a Normal CP or specialsubframe configuration 3, 4 and 8 (Normal CP), when the number of validresource elements in each PRB Pair is less than a threshold, theaggregation levels supported by the localized transmission mode are 2,4, 8, and 16, and the aggregation levels supported by the distributedtransmission mode are 2, 4, 8, 16, and 32. The aggregation levelssupported by both the localized transmission mode and the distributedtransmission mode are 2, 4, 8, and 16. In this case, the loweraggregation levels (namely, the first aggregation levels) are 2 and 4,and the higher aggregation levels (namely, the second aggregationlevels) are 8 and 16. In all other cases, the aggregation levels used bythe localized transmission mode are 1, 2, 4, and 8, and the aggregationlevels used by the distributed transmission mode are 1, 2, 4, 8, and 16.The aggregation levels supported by both the localized transmission modeand the distributed transmission mode are 1, 2, 4, and 8. In this case,the lower aggregation levels are 1 and 2, and the higher aggregationlevels are 4 and 8.

After completion of allocating at least one half of control channelcandidates at each aggregation level in the aggregation levels supportedby the control channel to be transmitted, remaining control channelcandidates at each aggregation level are allocated to different setsaccording to a predefined sequence of control channel sets and aposition of a start set at the aggregation level. The position of astart set at each aggregation level is related to the number of controlchannel candidates at the aggregation level and configuration of K_(L)and K_(D). For example, for a lower aggregation level, at least one halfof control channel candidates at the aggregation level are allocated toK_(L) sets of the localized transmission mode, and the position of thestart set at the aggregation level may be set in a set of the localizedtransmission mode in K_(L) sets of the localized transmission modeaccording to the number of control channel candidates at the aggregationlevel and K_(L) and K_(D).

Optionally, the UE may also allocate each control channel candidate toat least one set in the K sets according to the number of controlchannel candidates corresponding to each aggregation level and types ofthe sets. When the number of control channel candidates at theaggregation level is 2, remaining control channel candidates areallocated to all sets different from the type of the set to which thefirst control channel candidate is allocated. For example, if thenumbers of all control channel candidates corresponding to theaggregation levels supported by both the localized transmission mode andthe distributed transmission mode are 2, the first control channelcandidate is first allocated to a set in the K_(L) sets of the localizedtransmission mode, and the remaining one control channel candidate willbe allocated to a set in the K_(D) sets of the distributed transmissionmode.

According to the above method, for a lower aggregation level in theaggregation levels supported by both the localized transmission mode andthe distributed transmission mode, the UE may evenly allocate a half ofthe control channel candidates corresponding to the lower aggregationlevel to the K_(L) sets of the localized transmission mode, and allocatethe remaining half to different sets according to the predefinedsequence of control channel sets and the position of a start set at theaggregation level.

In the existing protocol, the aggregation levels supported by both thelocalized transmission mode and the distributed transmission mode may be1, 2, 4, and 8, or 2, 4, 8, and 16. Herein, assuming that theaggregation levels supported by both the localized transmission mode andthe distributed transmission mode are 1, 2, 4, and 8, for loweraggregation levels 1 and 2, one half of control channel candidatescorresponding to the aggregation levels 1 and 2 are first allocated toat least one set in the K_(L) sets, and the remaining half are allocatedto different sets according to the predefined sequence of controlchannel sets and the position of the start set at the aggregationlevels.

Assuming that aggregation level 1 or 2 corresponds to 6 control channelcandidates, the UE may allocate the first 3 control channel candidatesin the 6 control channel candidates corresponding to aggregation level 1or 2 to at least one set in the K_(L) sets. In this embodiment, theallocating the first 3 control channel candidates to at least one set inthe K_(L) sets includes evenly allocating the 3 control channelcandidates to the K_(L) sets, which means, a control channel candidateis allocated to each set sequentially in an incremental cyclic manner.The remaining 3 control channel candidates are allocated to differentsets according to the predefined sequence of control channel sets andthe position of the start set at the aggregation level. In theembodiment of the present application, K_(L) sets of the localizedtransmission mode are marked with 1, 2, . . . , and K_(L), and K_(D)sets of the distributed transmission mode are marked with 1, 2, . . . ,and K_(D). The allocating the remaining half of the control channelcandidates at the lower aggregation level 1 or 2 to different setsaccording to the predefined sequence of control channel sets and theposition of the start set at the aggregation level includes: allocatinga control channel candidate to each set sequentially from the start setaccording to the sequence from K_(L) sets 1, 2, . . . , and K_(L) of thelocalized transmission mode to K_(D) sets 1, 2, . . . , and K_(D) of thedistributed transmission mode, where the cyclic allocation is performeduntil the remaining half of the control channel candidates are allocatedcompletely.

For K=4, K_(L)=2, and K_(D)=2, when the start ePDCCH set is set 1 of thelocalized transmission mode, the result of allocating 6 control channelcandidates at aggregation level 1 or 2 to 4 ePDCCH sets is:

Set 1 of the Set 2 of the Set 1 of the Set 2 of the Localized LocalizedDistributed Distributed Transmission Transmission TransmissionTransmission Mode Mode Mode Mode 3 2 1 0

The first 3 control channel candidates are allocated to sets 1 and 2 ofthe localized transmission mode, where 2 control channel candidates arein set 1 of the localized transmission mode, and 1 control channelcandidate is in set 2 of the localized transmission mode. The last 3control channel candidates are sequentially allocated to sets 1 and 2 ofthe localized transmission mode and set 1 of the distributedtransmission mode from set 1 of the localized transmission mode.Therefore, the final result of allocating the 6 control channelcandidates to the 4 ePDCCH sets is: 3 control channel candidates are inset 1 of the localized transmission mode, 2 control channel candidatesare in set 2 of the localized transmission mode, and 1 control channelcandidate is in set 1 of the distributed transmission mode.

Likewise, for K=4, K_(L)=1, and K_(D)=3, when the start ePDCCH set isset 1 of the localized transmission mode, the result of allocating 6candidates at aggregation level 1 or 2 to 4 ePDCCH sets is:

Set 1 of the Set 1 of the Set 2 of the Set 3 of the LocalizedDistributed Distributed Distributed Transmission TransmissionTransmission Transmission Mode Mode Mode Mode 4 1 1 0

For K=4, K_(L)=3, and K_(D)=1, when the start ePDCCH set is set 3 of thelocalized transmission mode, the result of allocating 6 candidates ataggregation level 1 or 2 to 4 ePDCCH sets is:

Set 1 of the Set 2 of the Set 3 of the Set 1 of the Localized LocalizedLocalized Distributed Transmission Transmission TransmissionTransmission Mode Mode Mode Mode 1 2 2 1

For K=4, K_(L)=4, and K_(D)=0, when the start ePDCCH set is set 1 of thelocalized transmission mode, the result of allocating 6 candidates ataggregation level 1 or 2 to 4 ePDCCH sets is:

Set 1 of the Set 2 of the Set 3 of the Set 4 of the Localized LocalizedLocalized Localized Transmission Transmission Transmission TransmissionMode Mode Mode Mode 2 2 1 1

For K=4, K_(L)=0, and K_(D)=4, when the start ePDCCH set is set 1 of thedistributed transmission mode, the result of allocating 6 candidates ataggregation level 1 or 2 to 4 ePDCCH sets is:

Set 1 of the Set 2 of the Set 3 of the Set 4 of the DistributedDistributed Distributed Distributed Transmission TransmissionTransmission Transmission Mode Mode Mode Mode 2 2 1 1

For K=2, K_(L)=1, and K_(D)=1, assuming that the start ePDCCH set is set1 of the localized transmission mode, the result of allocating 6candidates at aggregation level 1 or 2 to 2 ePDCCH sets is:

Set 1 of the Localized Set 1 of the Distributed Transmission ModeTransmission Mode 5 1

For K=2, K_(L)=2, and K_(D)=0, assuming that the start ePDCCH set is set2 of the localized transmission mode, the result of allocating 6candidates at aggregation level 1 or 2 to 2 ePDCCH sets is:

Set 1 of the Localized Set 2 of the Localized Transmission ModeTransmission Mode 3 3

For K=2, K_(L)=0, and K_(D)=2, assuming that the start ePDCCH set is set1 of the distributed transmission mode, the result of allocating 6candidates at aggregation level 1 or 2 to 2 ePDCCH sets is:

Set 1 of the Distributed Set 2 of the Distributed Transmission ModeTransmission Mode 3 3

In the above method, after the UE allocates at least one half of thecontrol channel candidates corresponding to a lower aggregation level toat least one set in K_(L) sets of the localized transmission mode, theUE allocates a control channel candidate to each set sequentially fromthe start set according to the sequence from K_(L) sets 1, 2, . . . ,and K_(L) of the localized transmission mode to K_(D) sets 1, 2, . . . ,and K_(D) of the distributed transmission mode, where the cyclicallocation is performed until the remaining control channel candidatesare allocated completely. Optionally, the allocating the remainingcontrol channel candidates to different sets according to the predefinedsequence of control channel sets and the position of a start set at theaggregation level may also include: allocating a control channelcandidate in the sets of the localized transmission mode and the sets ofthe distributed transmission mode from the start set in a head/tailalternation manner according to the sequence of K_(L) sets 1, 2, . . . ,and K_(L) of the localized transmission mode and K_(D) sets 1, 2, . . ., and K_(D) of the distributed transmission mode, until the remaininghalf of the control channel candidates are allocated completely.

For K=4, K_(L)=1, and K_(D)=3, when the start ePDCCH set is set 1 of thelocalized transmission mode, the result of allocating 6 candidates ataggregation level 1 or 2 to 4 ePDCCH sets is:

Set 1 of the Set 1 of the Set 2 of the Set 3 of the LocalizedDistributed Distributed Distributed Transmission TransmissionTransmission Transmission Mode Mode Mode Mode 2 1 1 2

For K=4, K_(L)=1, and K_(D)=3, when the start ePDCCH set is set 2 of thelocalized transmission mode, the result of allocating 6 candidates ataggregation level 1 or 2 to 4 ePDCCH sets is:

Set 1 of the Set 1 of the Set 2 of the Set 3 of the LocalizedDistributed Distributed Distributed Transmission TransmissionTransmission Transmission Mode Mode Mode Mode 1 2 1 2

For a higher aggregation level in the aggregation levels supported byboth the localized transmission mode and the distributed transmissionmode, the UE may allocate at least one half of the control channelcandidates corresponding to the higher aggregation level to at least oneset in the K_(D) sets of the distributed transmission mode, and allocatethe remaining control channel candidates to different sets according tothe predefined sequence of control channel sets and the position of astart set at the aggregation level. In the embodiment of the presentapplication, the allocating at least one half of the control channelcandidates corresponding to the higher aggregation level to at least oneset in the K_(D) sets of the distributed transmission mode includes:allocating a control channel candidate to each set in the K_(D) sets ofthe distributed transmission mode sequentially according to the sequence1, 2, . . . , and K_(D), where the cyclic allocation is performed untilat least one half of the control channel candidates are allocatedcompletely. The allocating the remaining control channel candidates todifferent sets according to the predefined sequence of control channelsets and the position of a start set at the aggregation level includes:allocating one of the remaining control channel candidates to each setsequentially from the start set according to the reverse sequence fromK_(L) sets 1, 2, . . . , and K_(L) of the localized transmission mode toK_(D) sets 1, 2, . . . , and K_(D) of the distributed transmission mode,where the cyclic allocation is performed until the remaining half of thecontrol channel candidates are allocated completely. Preferably, whenthe number of control channel candidates at the aggregation level is 2,remaining control channel candidates are allocated to all sets differentfrom the type of the set to which the first control channel candidate isallocated. In other words, when the number of candidates at theaggregation level is 2, two control channel candidates are respectivelyallocated to a set in a region of the distributed transmission mode anda set in a region of localized transmission mode.

Herein, still assuming that the aggregation levels supported by both thelocalized transmission mode and the distributed transmission mode are 1,2, 4, and 8, for the higher aggregation levels 4 and 8, a half of thecontrol channel candidates corresponding to aggregation levels 4 and 8are first allocated to at least one set in the K_(D) sets of thedistributed transmission mode. In this embodiment, the first controlchannel candidate is allocated to one of the K_(D) sets, for example, acontrol channel candidate is allocated to each set sequentially in anincremental cyclic manner. The remaining half may be allocated to allsets different from the type of the set to which the first controlchannel candidate is allocated, namely, to a set in the K_(L) sets ofthe localized transmission mode.

For K=4, K_(L)=2, and K_(D)=2, when two control channel candidates arerespectively allocated to a set in the region of the distributedtransmission mode and a set in the region of the localized transmissionmode, the result of allocating 2 control channel candidates ataggregation level 4 or 8 to 4 ePDCCH sets is:

Set 1 of the Set 2 of the Set 1 of the Set 2 of the Localized LocalizedDistributed Distributed Transmission Transmission TransmissionTransmission Mode Mode Mode Mode 0 1 1 0

For K=4, K_(L)=2, and K_(D)=2, when the start set is set 1 of thedistributed transmission mode, the result of allocating 2 controlchannel candidates at aggregation level 4 or 8 to 4 ePDCCH sets is:

Set 1 of the Set 2 of the Set 1 of the Set 2 of the Localized LocalizedDistributed Distributed Transmission Transmission TransmissionTransmission Mode Mode Mode Mode 1 0 1 0

For K=2, K_(L)=1, and K_(D)=1, the result of allocating 2 controlchannel candidates at aggregation level 4 or 8 to 2 ePDCCH sets is:

Set 1 of the Localized Set 1 of the Distributed Transmission ModeTransmission Mode 1 1

In the above method, after the UE allocates at least one half of thecontrol channel candidates corresponding to a higher aggregation levelto at least one set in K_(D) sets of the distributed transmission mode,the UE allocates a control channel candidate to each set sequentiallyfrom the start set according to the sequence from K_(L) sets 1, 2, . . ., and K_(L) of the localized transmission mode to K_(D) sets 1, 2, . . ., and K_(D) of the distributed transmission mode, where the cyclicallocation is performed until the remaining control channel candidatesare allocated completely. Optionally, the allocating the remainingcontrol channel candidates to different sets according to the predefinedsequence of control channel sets and the position of a start set at theaggregation level may also include: allocating a control channelcandidate in the sets of the localized transmission mode and the sets ofthe distributed transmission mode from the start set in a head/tailalternation manner according to the sequence of K_(L) sets 1, 2, . . . ,and K_(L) of the localized transmission mode and K_(D) sets 1, 2, . . ., and K_(D) of the distributed transmission mode, until the remaininghalf of the control channel candidates are allocated completely.

For K=4, K_(L)=2, and K_(D)=2, when two control channel candidates arerespectively allocated to a set in the region of the distributedtransmission mode and a set in the region of the localized transmissionmode, the result of allocating 2 control channel candidates ataggregation level 4 or 8 to 4 ePDCCH sets is:

Set 1 of the Set 2 of the Set 1 of the Set 2 of the Localized LocalizedDistributed Distributed Transmission Transmission TransmissionTransmission Mode Mode Mode Mode 1 0 0 1

After obtaining the value of K configured by the eNB for the UE, the UEmay allocate the control channel candidates to at least one set in the Ksets. The allocation method may include 3 cases. In the third case, theallocating all control channel candidates at the aggregation levelssupported by both the localized transmission mode and the distributedtransmission mode to at least one set in the K_(D) sets of thedistributed transmission mode and at least one set in the K_(L) sets ofthe localized transmission mode when both the K_(L) and K_(D) arepositive integers, may also include:

determining, according to a ratio between the numbers of sets used forthe aggregation levels in K_(D) and K_(L), the number of control channelcandidates allocated to the K_(L) and K_(D) sets, at each aggregationlevel; or determining, according to a ratio between the total numbers ofphysical resource blocks in sets used for the aggregation levels inK_(D) and K_(L), the number of control channel candidates allocated tothe K_(L) and K_(D) sets, at each aggregation level; or determining,according to a ratio of the number of physical resource blocks of eachset in sets used for the aggregation levels in K_(D) and K_(L), thenumber of control channel candidates allocated to each set in the K_(L)and K_(D) sets, at each aggregation level.

After allocating all control channel candidates at the aggregationlevels supported by both the distributed transmission mode and thelocalized transmission mode to at least one set in the K_(D) sets of thedistributed transmission mode and at least one set in the K_(L) sets ofthe localized transmission mode, all control channel candidates at theaggregation level supported by only the distributed transmission mode orthe localized transmission mode are allocated to at least one set in theK_(D) sets of the distributed transmission mode or in the K_(L) sets ofthe localized transmission mode, which includes: determining, accordingto the number of sets used for the aggregation level in K_(D) or K_(L),the number of control channel candidates allocated to each set in theK_(L) or K_(D) sets, at the aggregation level; or determining, accordingto a ratio of the number of physical resource blocks of each set in setsused for the aggregation level in K_(D) or K_(L), the number of controlchannel candidates allocated to each set in the K_(L) or K_(D) sets, atthe aggregation level. For example, aggregation levels supported by thecontrol channel to be transmitted may be 1, 2, 4, 8, and 16, and mayalso be 2, 4, 8, 16, and 32, where an aggregation level supported byonly the distributed transmission mode is 16 or 32, and the UE mayallocate all control channel candidates at aggregation level 16 or 32 toat least one set in the K_(D) sets of the distributed transmission mode.Generally, the UE may allocate all control channel candidates ataggregation level 16 or 32 to one set in the K_(D) sets of thedistributed transmission mode. Optionally, the UE also determines,according to the number of sets used for the aggregation level 16 or 32in K_(D), the number of control channel candidates allocated to eachset, at the aggregation level 16 or 32, for example, when the number ofsets used for the aggregation level 16 or 32 is 2, and the number ofcontrol channel candidates is also 2, allocation is performedsequentially in a manner of placing one candidate in each set.Otherwise, allocation is performed by using the following methods:

Method 1: Firstly, assuming that the number of control channelcandidates corresponding to the aggregation level is M^((L)), and thenumber of sets is K, perform allocation, according to the number└M^((L))/K┘, for each set of the sets supporting the aggregation level,then place one of the remaining M^((L))−└M^((L))/K┘ candidatescyclically to each set sequentially until all candidates are completelyallocated. “└ ┘” means rounding up.

Method 2: According to a ratio of the number of physical resource blocksof each set supporting the aggregation level to the total number ofphysical resource blocks in all sets that support the aggregation level,first perform the following allocation in the set of the highest orlowest ratio: └M^((L))·(N_(i)/N_(total))┘, where N_(i) is the number ofphysical resource blocks in set i, and N_(total) is the total number ofphysical resource blocks in all the sets. Secondly, according to thismethod, place the remaining M^((L))−└M^((L))·(N_(i)/N_(total))┘candidates in a set of a next higher or next lower ratio in a recursivemanner until all candidates are allocated completely.

Method 3: Mark each set supporting the aggregation level L with s1, s2,s3, . . . , and sT. Firstly, allocate ci control channel candidates toset si according to the following formula, where the number ci may beindicated by:

$c_{i} = {\left\lfloor \frac{C_{L} \times N_{i}}{\sum\limits_{j = 1}^{T}\; N_{j}} \right\rfloor.}$

Place the remaining

$R = {C_{L} - {\sum\limits_{j = 1}^{T}\; c_{i}}}$control channel candidates in R sets according to a preset rule. HereinC_(L) is the number of control channel candidates corresponding to theaggregation level L.

The preset rule may be: sorting the R sets according to the number ofphysical resource block pairs included in each set, marking the sorted Rsets with s1, s2, s3, . . . , and sR, where assuming that the number ofphysical resource block pairs included in the set si is Ni, the sortedsets satisfy Ni≥Nj and i<=j, and placing one control channel candidatein each set of the R sets sequentially according to the sequence of s1,s2, . . . , and sR.

In the above method, the UE allocates all control channel candidates atthe aggregation levels supported by both the localized transmission modeand the distributed transmission mode in the aggregation levelssupported by the control channel to be transmitted to at least one setin the K_(D) sets of the distributed transmission mode and at least oneset in the K_(L) sets of the localized transmission mode; and allocatesall control channel candidates at the aggregation level supported byonly the distributed transmission mode or localized transmission mode toat least one set in the K_(D) sets of the distributed transmission modeor K_(L) sets of the localized transmission mode. Optionally, at eachaggregation level supported by the control channel to be transmitted,the numbers of control channel candidates allocated to the K_(L) sets ofthe localized transmission mode and the K_(D) sets of the distributedtransmission mode may be configured, and may also be obtained bycalculation, which means, the allocation is a function of at least oneof the number of control channel candidates at the aggregation level,the number K_(L) of sets of the localized transmission mode, and thenumber K_(D) of sets of the distributed transmission mode.

Optionally, the UE may receive the number of control channel candidatesat each aggregation level, which is higher-layer semi-staticallyconfigured by RRC signaling, in the K_(L) sets of the localizedtransmission mode and the K_(D) sets of the distributed transmissionmode. Preferably, when the number of available resource elementsincluded in each PRB pair is greater than or equal to a threshold (suchas 104), one configuration, as shown in the following tables, issemi-statically configured by RRC signaling for the UE:

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 1 3 1 2 4 2 4 1 1 8 1 1 16 0 2

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 1 3 1 2 3 3 4 1 1 8 1 1 16 0 2

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 1 3 1 2 5 1 4 1 1 8 1 1 16 0 2

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 1 3 1 2 6 0 4 1 1 8 1 1 16 0 2

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 1 2 2 2 3 3 4 1 1 8 1 1 16 0 2

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 1 2 2 2 4 2 4 1 1 8 1 1 16 0 2

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 1 2 2 2 5 1 4 1 1 8 1 1 16 0 2

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 1 2 2 2 6 0 4 1 1 8 1 1 16 0 2

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 1 4 1 2 4 2 4 1 1 8 1 1 16 0 1

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 1 4 1 2 3 3 4 1 1 8 1 1 16 0 1

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 1 4 1 2 5 1 4 1 1 8 1 1 16 0 1

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 1 4 1 2 6 0 4 1 1 8 1 1 16 0 1

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 1 4 1 2 6 0 4 1 1 8 1 1 16 0 1

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 1 3 2 2 3 3 4 1 1 8 1 1 16 0 1

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 1 3 2 2 4 2 4 1 1 8 1 1 16 0 1

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 1 3 2 2 5 1 4 1 1 8 1 1 16 0 1

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 1 3 2 2 6 0 4 1 1 8 1 1 16 0 1

Set of the Localized Set of the Distributed Aggregation LevelTransmission Mode Transmission Mode 1 5 0 2 6 0 4 1 1 8 1 1 16 0 1

Set of the Localized Set of the Distributed Aggregation LevelTransmission Mode Transmission Mode 1 4 0 2 6 0 4 1 1 8 1 1 16 0 2

When the number of available resource elements included in each PRB pairis less than a threshold (such as 104), one configuration, as shown inthe following tables, semi-statically configured by RRC signaling forthe terminal:

Set of the Localized Set of the Distributed Aggregation LevelTransmission Mode Transmission Mode 2 3 1 4 4 2 8 1 1 16 1 1 32 0 2

Set of the Localized Set of the Distributed Aggregation LevelTransmission Mode Transmission Mode 2 3 1 4 3 3 8 1 1 16 1 1 32 0 2

Set of the Localized Set of the Distributed Aggregation LevelTransmission Mode Transmission Mode 2 3 1 4 5 1 8 1 1 16 1 1 32 0 2

Set of the Localized Set of the Distributed Aggregation LevelTransmission Mode Transmission Mode 2 3 1 4 6 0 8 1 1 16 1 1 32 0 2

Set of the Localized Set of the Distributed Aggregation LevelTransmission Mode Transmission Mode 2 2 2 4 3 3 8 1 1 16 1 1 32 0 2

Set of the Localized Set of the Distributed Aggregation LevelTransmission Mode Transmission Mode 2 2 2 4 4 2 8 1 1 16 1 1 32 0 2

Set of the Localized Set of the Distributed Aggregation LevelTransmission Mode Transmission Mode 2 2 2 4 5 1 8 1 1 16 1 1 32 0 2

Set of the Localized Set of the Distributed Aggregation LevelTransmission Mode Transmission Mode 2 2 2 4 6 0 8 1 1 16 1 1 32 0 2

Set of the Localized Set of the Distributed Aggregation LevelTransmission Mode Transmission Mode 2 4 1 4 4 2 8 1 1 16 1 1 32 0 1

Set of the Localized Set of the Distributed Aggregation LevelTransmission Mode Transmission Mode 2 4 1 4 3 3 8 1 1 16 1 1 32 0 1

Set of the Localized Set of the Distributed Aggregation LevelTransmission Mode Transmission Mode 2 4 1 4 5 1 8 1 1 16 1 1 32 0 1

Set of the Localized Set of the Distributed Aggregation LevelTransmission Mode Transmission Mode 2 4 1 4 6 0 8 1 1 16 1 1 32 0 1

Set of the Localized Set of the Distributed Aggregation LevelTransmission Mode Transmission Mode 2 4 1 4 6 0 8 1 1 16 1 1 32 0 1

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 2 3 2 4 3 3 8 1 1 16 1 1 32 0 1

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 2 3 2 4 4 2 8 1 1 16 1 1 32 0 1

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 2 3 2 4 5 1 8 1 1 16 1 1 32 0 1

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 2 3 2 4 6 0 8 1 1 16 1 1 32 0 1

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 2 5 0 4 6 0 8 1 1 16 1 1 32 0 1

Aggregation Set of the Localized Set of the Distributed LevelTransmission Mode Transmission Mode 2 4 0 4 6 0 8 1 1 16 1 1 32 0 2

Optionally, according to the allocation shown in the above tables, theUE may perform proportional allocation of the candidates betweendifferent sets according to the number of PRB pairs included in each setof a set type, for example, when the number of control channelcandidates allocated to the K_(L)=2 sets of the localized transmissionmode is 3, and the numbers of PRB Pairs included in two sets are 2 and 4respectively, the 3 control channel candidates are respectivelyallocated to each set according to the ratio of the number of includedPRB Pairs, namely, 1:2. Of course, when the number of control channelcandidates is 4, and allocation cannot be performed according to theratio 1:2, allocation may be performed according to the ratioceil(4/(1+2))−1=1:ceil(4*2/(1+2))=3. Ceil means rounding up.

Optionally, the UE may also obtain, by calculation, the number ofcontrol channel candidates allocated to the K_(L) sets of the localizedtransmission mode and the K_(D) sets of the distributed transmissionmode. Preferably, for a lower aggregation level supported by the controlchannel to be transmitted, when the number of control channel candidatescorresponding to the lower aggregation level is an even number, thenumber of control channel candidates allocated to the K_(L) sets of thelocalized transmission mode meets the following formula:

${{M^{(L)}\text{/}2} + \left\lfloor {{\frac{K_{L}}{K_{L} + K_{D}} \cdot M^{(L)}}\text{/}2} \right\rfloor};$and the number of control channel candidates allocated to the K_(D) setsof the localized transmission mode meets the following formula:

${{M^{(L)}\text{/}2} - \left\lfloor {{\frac{K_{L}}{K_{L} + K_{D}} \cdot M^{(L)}}\text{/}2} \right\rfloor};$when the number of control channel candidates corresponding to the loweraggregation level is an odd number, the number of control channelcandidates allocated to the K_(L) sets of the localized transmissionmode meets the following formula:

${{\left( {M^{(L)} + 1} \right)\text{/}2} + \left\lfloor {{\frac{K_{L}}{K_{L} + K_{D}} \cdot \left( {M^{(L)} - 1} \right)}\text{/}2} \right\rfloor};$and the number of control channel candidates allocated to the K_(D) setsof the localized transmission mode meets the following formula:

${{\left( {M^{(L)} - 1} \right)\text{/}2} - \left\lfloor {{\frac{K_{L}}{K_{L} + K_{D}} \cdot \left( {M^{(L)} - 1} \right)}\text{/}2} \right\rfloor};$and an allocation ratio of all candidates at aggregation levelssupported by the control channel to be transmitted, except the loweraggregation level, is 1:1 between the K_(L) sets of the localizedtransmission mode and the K_(D) sets of the distributed transmissionmode. When the aggregation levels supported by the control channel to betransmitted are 1, 2, 4, 8, and 16, the lower aggregation levels are 1and 2; when the aggregation levels supported by the control channel tobe transmitted are 2, 4, 8, 16, and 32, the lower aggregation levels are2 and 4.

Based on the higher-layer semi-statically configured or the calculatednumber of control channel candidates at each aggregation level in theK_(L) sets of the localized transmission mode and K_(D) sets of thedistributed transmission mode, for each aggregation level, when thenumber of control channel candidates configured for the K_(L) sets ofthe localized transmission mode is greater than 1, the number of controlchannel candidates in each set is determined according to the number ofphysical resource blocks included in each set of the localizedtransmission mode; or when the number of control channel candidatesconfigured for the K_(D) sets of the distributed transmission mode isgreater than 1, the number of control channel candidates in each set isdetermined according to the number of physical resource blocks includedin each set of the distributed transmission mode.

Optionally, the UE may perform proportional allocation of the abovecandidates between different sets according to the number of PRB pairsincluded in each set of a set type, for example, when the number ofcontrol channel candidates allocated to the K_(L)=2 sets of thelocalized transmission mode is 3, and the numbers of PRB Pairs includedin two sets are 2 and 4 respectively, the 3 control channel candidatesare respectively allocated to each set according to the ratio of thenumber of included PRB Pairs, namely, 1:2. Of course, when the number ofcontrol channel candidates is 4, and allocation cannot be performedaccording to the ratio 1:2, allocation may be performed according to theratio ceil(4/(1+2))−1=1:ceil(4*2/(1+2))=3. Ceil means rounding up.

Further, there may be a binding relationship between the number of PRBPairs specific to the aggregation level and control channel candidates.For example, when the aggregation level is 4 (the corresponding numberof control channel candidates is 2), and the number of sets is 4, 2 setsmay be first selected from the 4 sets and then allocation and binding ofthe control channel candidates are performed according to the number ofPRB pairs included in the 2 sets. Herein the sets may be selectedsequentially according to the ascending order of PRB Pair numbers.

Optionally, the allocating the control channel candidates at eachaggregation level to at least one set in the K sets according toaggregation levels supported by the control channel to be transmitted,the number of control channel candidates corresponding to eachaggregation level, the K sets for transmitting the control channel, andtypes of the sets, includes: allocating all control channel candidatesat one or two aggregation levels to at least one set in the K sets.

Optionally, the UE may bind aggregation levels with the K sets, whichmeans, all candidates at each aggregation level are allocated to atleast one specific set, and all candidates at each aggregation level ina transmission mode correspond to one or more ePDCCH sets in the regionof the set of the transmission mode. When 4 control channel candidatesof the localized transmission mode and 2 control channel candidates ofthe distributed transmission mode at aggregation levels 1 and 2 areallocated, the UE may allocate the corresponding 4 control channelcandidates of the localized transmission mode to the first set of thelocalized transmission mode in the K_(L) sets of the localizedtransmission mode, and allocate the corresponding 2 control channelcandidates of the distributed transmission mode to the first set of thedistributed transmission mode in the K_(D) sets of the distributedtransmission mode. When 1 candidate of the localized transmission modeand 1 candidate of the distributed transmission mode at aggregationlevels 4 and 8 are allocated, the UE may allocate the corresponding 1candidate of the localized transmission mode to the second set in theK_(L) sets of the localized transmission mode, and allocate thecorresponding 1 candidate of the distributed transmission mode to thesecond set in the K_(D) sets of the distributed transmission mode. Allcontrol channel candidates at aggregation levels 16 and 32 are allocatedto the third specific set in the region of the distributed transmissionmode, where the number of PRB Pairs included in the specific set is atleast 4 or 8.

Binding between the aggregation levels and the K sets may reducereservations of PUCCH ACK/NCK resource positions, because the number ofreserved PUCCH ACK/NCK resources in each set may be determined accordingto the bound aggregation levels. For example, a set includes 8 PRBpairs, and 32 eCCEs are specially used for placing candidates ataggregation level 16 or/and 32; therefore, when ACK/NACK resources arereserved, only two ACK/NACK resources, instead of 32 resources, need tobe reserved.

Control channel candidates at each aggregation level are placed in eachset according to a sequence and a reverse sequence alternately. Forexample, for candidates at aggregation level 1, one candidate is placedin each PRB Pair according to the ascending order of the PRB Pairnumbers, and for candidates at aggregation level 2, one candidate isplaced in each PRB Pair according to the descending order of the PRBPair numbers. Likewise, by analogy, all control channel candidates ataggregation levels 4, 8, and 16 may be placed in the corresponding sets.

The K_(L) and K_(D) for transmitting the control channel are configured,and the number of physical resource block pairs included in each set isconfigured; or the K_(L) and K_(D) for transmitting the control channelare fixed, the number of physical resource block pairs included in eachset is configured, and allocation of all control channel candidates ateach aggregation level to the K_(L) and K_(D) sets is fixed.

Optionally, a rule for determining the number of control channelcandidates corresponding to the aggregation levels that are supported bythe control channel to be transmitted is as follows:

When only the sets of the localized transmission mode exist, namely,K_(L)>0 and K_(D)=0, there may be the following two cases for the numberof control channel candidates corresponding to each aggregation level.

1. Given an extended cyclic prefix and a normal cyclic prefix, andnormal subframe/special subframe configurations 3, 4, and 8, whenn_(EPDCCH) the number of available resource elements in each PRB Pair,is greater than or equal to 104 (n_(EPDCCH)≥104), the number of controlchannel candidates corresponding to each aggregation level is shown inthe following table:

Search Space S_(k) ^((L)) Aggregation Size Number M^((L)) of Type LevelL [in eCCEs] ePDCCH Candidates UE-Specific 1 6 6 2 12 6 4 8 2 8 16 2

2. Given a normal cyclic prefix and normal subframe/special subframeconfigurations 3, 4, and 8, when n_(EPDCCH), the number of availableresource elements in each PRB Pair, is less than 104 (n_(EPDCCH)<104),the number of control channel candidates corresponding to eachaggregation level is shown in the following table:

Search Space S_(k) ^((L)) Aggregation Size Number M^((L)) of Type LevelL [in eCCEs] ePDCCH Candidates UE-Specific 2 12 6 4 24 6 8 16 2 16 32 2

When only the sets of the distributed transmission mode exist, namely,K_(L)=0 and K_(D)>0, there may be the following cases for the number ofcontrol channel candidates corresponding to each aggregation level:

Given an extended cyclic prefix and a normal cyclic prefix, and normalsubframe/special subframe configurations 3, 4, and 8, when n_(EPDCCH),the number of available resource elements in each PRB Pair, is greaterthan or equal to 104 (n_(EPDCCH)≥104), the number of control channelcandidates corresponding to each aggregation level is shown in thefollowing tables:

Search Space S_(k) ^((L)) Aggregation Size Number M^((L)) of Type LevelL [in eCCEs] ePDCCH Candidates UE-Specific 1 4 4 2 12 6 4 8 2 8 16 2

Search Space S_(k) ^((L)) Aggregation Size Number M^((L)) of Type LevelL [in eCCEs] ePDCCH Candidates 16 32 2

Search Space S_(k) ^((L)) Aggregation Size Number M^((L)) of Type LevelL [in eCCEs] ePDCCH Candidates UE-Specific 1 5 5 2 12 6 4 8 2 8 16 2 1616 1

Given a normal cyclic prefix and normal subframe/special subframeconfigurations 3, 4, and 8, when n_(EPDCCH) the number of availableresource elements in each PRB Pair, is less than 104 (n_(EPDCCH)<104),the UE blindly detects EPDCCH candidates.

Search Space S_(k) ^((L)) Aggregation Size Number M^((L)) of Type LevelL [in eCCEs] ePDCCH Candidates UE-Specific 2 8 4 4 24 6 8 16 2 16 32 232 64 2

Search Space S_(k) ^((L)) Aggregation Size Number M^((L)) of Type LevelL [in eCCEs] ePDCCH Candidates UE-Specific 2 10 5 4 24 6 8 16 2 16 32 232 32 1

The allocation solution considers that control information correspondingto main transmission modes in Rel-11 is usually large and that onepurpose of introducing the ePDCCH is to enhance coverage. Therefore,after a new higher aggregation level is introduced for the ePDCCH, thenumbers of candidates at other aggregation levels remain unchanged, and1 or 2 candidates at aggregation level 1 are transferred to the addedhigher aggregation level.

When the sets of the localized transmission mode and the sets of thedistributed transmission mode exist, namely, K_(L)>0 and K_(D)>0, theremay be the following cases for the number of control channel candidatescorresponding to each aggregation level.

Given an extended cyclic prefix and a normal cyclic prefix, and normalsubframe/special subframe configurations 3, 4, and 8, when n_(EPDCCH)the number of available resource elements in each PRB Pair, is greaterthan or equal to 104 (n_(EPDCCH)≥104), the number of control channelcandidates corresponding to each aggregation level is shown in thefollowing table:

Search Space S_(k) ^((L)) Aggregation Size Number M^((L)) of Type LevelL [in eCCEs] ePDCCH Candidates UE-Specific 1 6 6L 2 12 6L 4 1 1L 8 162(1L + 1D) 16 16 1D

Given a normal cyclic prefix and normal subframe/special subframeconfigurations 3, 4, and 8, when n_(EPDCCH), the number of availableresource elements in each PRB Pair, is less than 104 (n_(EPDCCH)<104),the number of control channel candidates corresponding to eachaggregation level is shown in the following table:

Search Space S_(k) ^((L)) Aggregation Size Number M^((L)) of Type LevelL [in eCCEs] ePDCCH Candidates UE-Specific 2 12 6L 4 24 6L 8 16 1L 16 322(1L + 1D) 32 32 1L

Optionally, the maximum value of the number K of sets of all UEs may befixed to one of 2, 3, 4, and 6, and the number of PRB pairs included ineach set changes according to scenarios. For example, when the number ofusers in a cell or the number of multiplexed users in each setincreases, the number of PRB pairs included in each set also increases.In this case, the UE may cyclically map the corresponding number ofcontrol channel candidates corresponding to each aggregation levelsequentially according to the sequence of the K sets until thecorresponding number of control channel candidates corresponding to eachaggregation level are allocated completely.

This solution may simplify the allocation of all control channelcandidates at each aggregation level among K sets (especially in a casewhere both a set of the localized transmission mode and a set of thedistributed transmission mode exist). For example, when the maximumnumber K of sets is 2, one is a set of the localized transmission mode,and the other is a set of the distributed transmission mode. In thiscase, all candidates at each aggregation level may be allocated to thetwo sets respectively according to one half of the number.

An embodiment of the present application further provides an apparatusfor allocating control channel candidates. As shown in FIG. 2, theapparatus includes a determining unit 201 and an allocating unit 202.

The determining unit 201 is configured to determine K sets fortransmitting a control channel, where each set in the K sets includes atleast one physical resource block pair, and K is a positive integergreater than 0; and the allocating unit 202 is configured to allocate,according to at least one of aggregation levels supported by the controlchannel, the number of control channel candidates corresponding to eachaggregation level, the K sets for transmitting the control channel, andtypes of the sets, each control channel candidate to at least one set inthe K sets determined by the determining unit 201.

The K sets for transmitting the control channel include a set of alocalized transmission mode and a set of a distributed transmissionmode, where the number of sets of the localized transmission mode isK_(L), and the number of sets of the distributed transmission mode isK_(D), where K_(L)+K_(D)=K, and K_(L) and K_(D) are integers greaterthan or equal to 0; and the aggregation levels supported by the controlchannel include one or more of the following levels: aggregation levelssupported by the localized transmission mode, aggregation levelssupported by the distributed transmission mode, and common aggregationlevels supported by both the localized transmission mode and thedistributed transmission mode.

Optionally, the allocating unit 202 is specifically configured to: whenK_(L) is a positive integer, allocate all control channel candidates atthe aggregation levels supported by the localized transmission mode toat least one of the K_(L) sets; or when K_(D) is a positive integer,allocate all control channel candidates at the aggregation levelssupported by the distributed transmission mode to at least one of theK_(D) sets; or when both K_(L) and K_(D) are positive integers, allocateall control channel candidates at each aggregation level in theaggregation levels supported by both the localized transmission mode andthe distributed transmission mode to at least one of the K_(D) sets andat least one of the K_(L) sets.

The allocating unit 202 being configured to allocate all control channelcandidates at each aggregation level in the aggregation levels supportedby both the localized transmission mode and the distributed transmissionmode to at least one of the K_(D) sets and at least one of the K_(L)sets when both K_(L) and K_(D) are positive integers, includes:allocating at least one half of all control channel candidates at eachfirst aggregation level in the aggregation levels supported by both thelocalized transmission mode and the distributed transmission mode to atleast one of the K_(L) sets; and allocating at least one half of allcontrol channel candidates at each second aggregation level in theaggregation levels supported by both the localized transmission mode andthe distributed transmission mode to at least one of the K_(D) sets.

Herein, when the aggregation levels supported by both the localizedtransmission mode and the distributed transmission mode are 1, 2, 4, and8, the first aggregation levels are 1 and 2, and the second aggregationlevels are 4 and 8; and when the aggregation levels supported by boththe localized transmission mode and the distributed transmission modeare 2, 4, 8, and 16, the first aggregation levels are 2 and 4, and thesecond aggregation levels are 8 and 16. Remaining control channelcandidates at each aggregation level are allocated to different setsaccording to a predefined sequence of control channel sets and/or aposition of a start set at the aggregation level. The position of astart set at each aggregation level is related to the number of controlchannel candidates at the aggregation level and configuration of K_(L)and K_(D).

Optionally, when the number of control channel candidates at theaggregation level is 2, remaining control channel candidates are notplaced in any set corresponding to a transmission mode of a firstcontrol channel candidate.

The allocating unit 202 being configured to allocate all control channelcandidates at an aggregation level supported by only the distributedtransmission mode or the localized transmission mode to at least one setin the K_(D) sets of the distributed transmission mode or in the K_(L)sets of the localized transmission mode, includes: determining,according to the number of sets used for the aggregation level in K_(D)or K_(L), the number of control channel candidates allocated to each setin the K_(D) or K_(L) sets, at the aggregation level; or determining,according to a ratio of the number of physical resource blocks of eachset in sets used for the aggregation level in K_(D) or K_(L), the numberof control channel candidates allocated to each set in the K_(D) orK_(L) sets, at the aggregation level.

The allocating unit 202 being configured to allocate all control channelcandidates at each aggregation level in the aggregation levels supportedby both the localized transmission mode and the distributed transmissionmode to at least one of the K_(D) sets and at least one of the K_(L)sets when both K_(L) and K_(D) are positive integers, includes:determining, according to a ratio between the numbers of sets used forthe aggregation level in K_(D) and K_(L), the numbers of control channelcandidates allocated to the K_(L) and K_(D) sets, at each aggregationlevel; or determining, according to a ratio between the total numbers ofphysical resource blocks in sets used for the aggregation level in K_(D)and K_(L), the numbers of control channel candidates allocated to theK_(L) and K_(D) sets, at each aggregation level; or determining,according to a ratio of the number of physical resource blocks of eachset in sets used for the aggregation level in K_(D) and K_(L), thenumber of control channel candidates allocated to each set in the K_(L)and K_(D) sets, at each aggregation level.

At each aggregation level, the numbers of control channel candidatesallocated to the K_(L) and K_(D) sets are configured. The configurationis a higher-layer semi-static configuration.

At each aggregation level, when the number of control channel candidatesconfigured for the K_(L) (greater than 1) sets is greater than 1, theallocating unit 202 is configured to determine the number of controlchannel candidates in each set according to the number of physicalresource blocks included in each set that can support the aggregationlevel in the K_(L) sets or the number of sets that can support theaggregation level in the K_(L) sets, or when the number of controlchannel candidates configured for the K_(D) (greater than 1) sets isgreater than 1, the allocating unit 202 is configured to determine thenumber of control channel candidates in each set according to the numberof physical resource blocks included in each set that can support theaggregation level in the K_(D) sets or the number of sets that cansupport the aggregation level in the K_(D) sets.

At each aggregation level supported by the control channel to betransmitted, the number of control channel candidates allocated to theK_(L) sets of the localized transmission mode and the number of controlchannel candidates allocated to the K_(D) sets of the distributedtransmission mode are functions of at least one of the number of controlchannel candidates at the aggregation level, the number K_(L) of sets ofthe localized transmission mode, and the number K_(D) of sets of thedistributed transmission mode.

When the number of control channel candidates corresponding to theaggregation levels supported by both the localized transmission mode andthe distributed transmission mode is an even number, the number ofcontrol channel candidates allocated to the K_(L) sets of the localizedtransmission mode meets the following formula:

${{M^{(L)}\text{/}2} + \left\lfloor {{\frac{K_{L}}{K_{L} + K_{D}} \cdot M^{(L)}}\text{/}2} \right\rfloor};$and the number of control channel candidates allocated to the K_(D) setsof the distributed transmission mode meets the following formula:

${M^{(L)}\text{/}2} - {\left\lfloor {{\frac{K_{L}}{K_{L} + K_{D}} \cdot M^{(L)}}\text{/}2} \right\rfloor.}$When the number of control channel candidates corresponding to the loweraggregation levels is an odd number, the number of control channelcandidates allocated to the K_(L) sets of the localized transmissionmode meets the following formula:

${{\left( {M^{(L)} + 1} \right)\text{/}2} + \left\lfloor {{\frac{K_{L}}{K_{L} + K_{D}} \cdot \left( {M^{(L)} - 1} \right)}\text{/}2} \right\rfloor};$and the number of control channel candidates allocated to the K_(D) setsof the distributed transmission mode meets the following formula:

${{{\left( {M^{(L)} - 1} \right)\text{/}2} - \left\lfloor {{\frac{K_{L}}{K_{L} + K_{D}} \cdot \left( {M^{(L)} - 1} \right)}\text{/}2} \right\rfloor};}.$An allocation ratio of all candidates at aggregation levels where thenumber of control channel candidates is 2, is 1:1 between the K_(L) setsof the localized transmission mode and the K_(D) sets of the distributedtransmission mode.

The allocating unit 202 is configured to determine that at least one setin the K sets for transmitting the control channel is used to allocatecontrol channel candidates at one or two aggregation levels.

A rule for determining aggregation levels that can be supported by thecontrol channel to be transmitted includes:

-   -   when the total number of aggregation levels that can be        supported by the control channel is N, obtaining, according to        the number of valid physical resource elements included in each        physical resource block pair, k (k<=N) aggregation levels in the        N aggregation levels as aggregation levels of the control        channel to be transmitted, or    -   configuring, semi-statically through RRC signaling, k (k<=N)        aggregation levels in the N aggregation levels as aggregation        levels that can be supported by the control channel to be        transmitted.

A form of semi-static configuration through RRC signaling is a bitmap.

If the number of aggregation levels of the control channel to betransmitted is N, the numbers of control channel candidatescorresponding to any p (p<=4) aggregation levels in 4 aggregation levels(1, 2, 4, 8) in an original protocol are respectively configured forcorresponding aggregation levels in the N aggregation levels of thecontrol channel to be transmitted, and the numbers of control channelcandidates corresponding to remaining (4-p) aggregation levels in the 4aggregation levels (1, 2, 4, 8) in the original protocol arecorrespondingly configured for remaining N-p aggregation levels in the Naggregation levels of the control channel to be transmitted.

Optionally, the apparatus includes a detecting unit. When theaggregation levels supported by the control channel to be transmittedinclude 32, and the number of available resource elements in eachphysical resource block pair except resource elements of other signals,such as a CRS, a DMRS, a CSI-RS, a PDCCH, is greater than or equal to72, the detecting unit does not detect control channel candidates ataggregation level 32; otherwise, the detecting unit detects the controlchannel candidates at aggregation level 32; or, when the aggregationlevels supported by the control channel to be transmitted do not include32, and the number of available resource elements in each physicalresource block pair except resource elements of other signals, such as aCRS, a DMRS, a CSI-RS, a PDCCH, is less than 72, the detecting unitdetects control channel candidates at aggregation level 8.

When the control channel to be transmitted is transmitted with anextended cyclic prefix, and the supported aggregation levels include 16,and the number of available resource elements in each physical resourceblock pair except resource elements of other signals, such as a CRS, aDMRS, a CSI-RS, a PDCCH, is greater than or equal to 72, the detectingunit does not detect control channel candidates at aggregation level 16;otherwise, the detecting unit detects the control channel candidates ataggregation level 16; or, when the control channel to be transmitted istransmitted with an extended cyclic prefix, and the supportedaggregation levels do not include 16, and the number of availableresource elements in each physical resource block pair except resourceelements of other signals, such as a CRS, a DMRS, a CSI-RS, a PDCCH, isless than 72, the detecting unit detects PDCCH candidates at aggregationlevel 8.

The K_(L) and K_(D) for transmitting the control channel are configured,and the number of physical resource block pairs included in each set isconfigured; or the K_(L) and K_(D) for transmitting the control channelare fixed, the number of physical resource block pairs included in eachset is configured, and allocation of all control channel candidates ateach aggregation level to the K_(L) and K_(D) sets is fixed.

Herein the configuration refers to parameters configured by the basestation for the UE through higher-layer signaling, which means, valuesof the K_(L) and K_(D) and the number of physical resource block pairsincluded in each set may all be configured by the base station for theUE.

An embodiment of the present application further provides an apparatusfor allocating control channel candidates. As shown in FIG. 3, theapparatus includes a receiver 32, a transmitter 31, a memory 33, and aprocessor 34 that is connected to the receiver 31, the transmitter 32,and the memory 33, where the receiver may be configured to receivehigher-layer signaling sent by a base station. The memory stores a groupof program codes, and the processor invokes the program codes in thememory to perform operations.

The processor 34 is configured to determine K sets for transmitting acontrol channel, where each set in the K sets includes at least onephysical resource block pair, and K is a positive integer greater than0; the processor 34 is configured to allocate, according to at least oneof aggregation levels supported by the control channel, the number ofcontrol channel candidates corresponding to each aggregation level, theK sets for transmitting the control channel, and types of the sets, eachcontrol channel candidate to at least one set in the K sets determinedby the processor 34.

The K sets for transmitting the control channel include a set of alocalized transmission mode and a set of a distributed transmissionmode, where the number of sets of the localized transmission mode isK_(L), and the number of sets of the distributed transmission mode isK_(D), where K_(L)+K_(D)=K, and K_(L) and K_(D) are integers greaterthan or equal to 0; and the aggregation levels supported by the controlchannel include one or more of the following levels: aggregation levelssupported by the localized transmission mode, aggregation levelssupported by the distributed transmission mode, and common aggregationlevels supported by both the localized transmission mode and thedistributed transmission mode.

Optionally, the processor 34 is specifically configured to: when K_(L)is a positive integer, allocate all control channel candidates at theaggregation levels supported by the localized transmission mode to atleast one of the K_(L) sets; or when K_(D) is a positive integer,allocate all control channel candidates at the aggregation levelssupported by the distributed transmission mode to at least one of theK_(D) sets; or when both K_(L) and K_(D) are positive integers, allocateall control channel candidates at each aggregation level in theaggregation levels supported by both the localized transmission mode andthe distributed transmission mode to at least one of the K_(D) sets andat least one of the K_(L) sets.

The processor 34 being configured to allocate all control channelcandidates at each aggregation level in the aggregation levels supportedby both the localized transmission mode and the distributed transmissionmode to at least one of the K_(D) sets and at least one of the K_(L)sets when both K_(L) and K_(D) are positive integers, includes:allocating at least one half of all control channel candidates at eachfirst aggregation level in the aggregation levels supported by both thelocalized transmission mode and the distributed transmission mode to atleast one of the K_(L) sets; and allocating at least one half of allcontrol channel candidates at each second aggregation level in theaggregation levels supported by both the localized transmission mode andthe distributed transmission mode to at least one of the K_(D) sets.

Herein, when the aggregation levels supported by both the localizedtransmission mode and the distributed transmission mode are 1, 2, 4, and8, the first aggregation levels are 1 and 2, and the second aggregationlevels are 4 and 8; and when the aggregation levels supported by boththe localized transmission mode and the distributed transmission modeare 2, 4, 8, and 16, the first aggregation levels are 2 and 4, and thesecond aggregation levels are 8 and 16. Remaining control channelcandidates at each aggregation level are allocated to different setsaccording to a predefined sequence of control channel sets and/or aposition of a start set at the aggregation level. The position of astart set at each aggregation level is related to the number of controlchannel candidates at the aggregation level and configuration of K_(L)and K_(D).

Optionally, when the number of control channel candidates at theaggregation level is 2, remaining control channel candidates are notplaced in any set corresponding to a transmission mode of a firstcontrol channel candidate.

The processor 34 being configured to allocate all control channelcandidates at an aggregation level supported by only the distributedtransmission mode or the localized transmission mode to at least one setin the K_(D) sets of the distributed transmission mode or in the K_(L)sets of the localized transmission mode, includes: determining,according to the number of sets used for the aggregation level in K_(D)or K_(L), the number of control channel candidates allocated to each setin the K_(D) or K_(L) sets, at the aggregation level; or determining,according to a ratio of the number of physical resource blocks of eachset in sets used for the aggregation level in K_(D) or K_(L), the numberof control channel candidates allocated to each set in the K_(D) orK_(L) sets, at the aggregation level.

The processor 34 being configured to allocate all control channelcandidates at each aggregation level in the aggregation levels supportedby both the localized transmission mode and the distributed transmissionmode to at least one of the K_(D) sets and at least one of the K_(L)sets when both K_(L) and K_(D) are positive integers, includes:determining, according to a ratio between the numbers of sets used forthe aggregation level in K_(D) and K_(L), the numbers of control channelcandidates allocated to the K_(L) and K_(D) sets, at each aggregationlevel; or determining, according to a ratio between the total numbers ofphysical resource blocks in sets used for the aggregation level in K_(D)and K_(L), the numbers of control channel candidates allocated to theK_(L) and K_(D) sets, at each aggregation level; or determining,according to a ratio of the number of physical resource blocks of eachset in sets used for the aggregation level in K_(D) and K_(L), thenumber of control channel candidates allocated to each set in the K_(L)and K_(D) sets, at each aggregation level.

At each aggregation level, the numbers of control channel candidatesallocated to the K_(L) and K_(D) sets are configured. The configurationis a higher-layer semi-static configuration.

At each aggregation level, when the number of control channel candidatesconfigured for the K_(L) (greater than 1) sets is greater than 1, theprocessor 34 is configured to determine the number of control channelcandidates in each set according to the number of physical resourceblocks included in each set that can support the aggregation level inthe K_(L) sets or the number of sets that can support the aggregationlevel in the K_(L) sets, or when the number of control channelcandidates configured for the K_(D) (greater than 1) sets is greaterthan 1, the processor 34 is configured to determine the number ofcontrol channel candidates in each set according to the number ofphysical resource blocks included in each set that can support theaggregation level in the K_(D) sets or the number of sets that cansupport the aggregation level in the K_(D) sets.

At each aggregation level supported by the control channel to betransmitted, the number of control channel candidates allocated to theK_(L) sets of the localized transmission mode and the number of controlchannel candidates allocated to the K_(D) sets of the distributedtransmission mode are functions of at least one of the number of controlchannel candidates at the aggregation level, the number K_(L) of sets ofthe localized transmission mode, and the number K_(D) of sets of thedistributed transmission mode.

When the number of control channel candidates corresponding to theaggregation levels supported by both the localized transmission mode andthe distributed transmission mode is an even number, the number ofcontrol channel candidates allocated to the K_(L) sets of the localizedtransmission mode meets the following formula:

${{M^{(L)}\text{/}2} + \left\lfloor {{\frac{K_{L}}{K_{L} + K_{D}} \cdot M^{(L)}}\text{/}2} \right\rfloor};$and the number of control channel candidates allocated to the K_(D) setsof the distributed transmission mode meets the following formula:

${M^{(L)}\text{/}2} - {\left\lfloor {{\frac{K_{L}}{K_{L} + K_{D}} \cdot M^{(L)}}\text{/}2} \right\rfloor.}$When the number of control channel candidates corresponding to the loweraggregation levels is an odd number, the number of control channelcandidates allocated to the K_(L) sets of the localized transmissionmode meets the following formula:

${{\left( {M^{(L)} + 1} \right)\text{/}2} + \left\lfloor {{\frac{K_{L}}{K_{L} + K_{D}} \cdot \left( {M^{(L)} - 1} \right)}\text{/}2} \right\rfloor};$and the number of control channel candidates allocated to the K_(D) setsof the distributed transmission mode meets the following formula:

${\left( {M^{(L)} - 1} \right)\text{/}2} - {\left\lfloor {{\frac{K_{L}}{K_{L} + K_{D}} \cdot \left( {M^{(L)} - 1} \right)}\text{/}2} \right\rfloor.}$An allocation ratio of all candidates at aggregation levels where thenumber of control channel candidates is 2, is 1:1 between the K_(L) setsof the localized transmission mode and the K_(D) sets of the distributedtransmission mode.

The processor 34 is configured to determine that at least one set in theK sets for transmitting the control channel is used to allocate controlchannel candidates at one or two aggregation levels.

A rule for determining aggregation levels that can be supported by thecontrol channel to be transmitted includes:

when the total number of aggregation levels that can be supported by thecontrol channel is N, obtaining, according to the number of validphysical resource elements included in each physical resource blockpair, k (k<=N) aggregation levels in the N aggregation levels asaggregation levels of the control channel to be transmitted, or

configuring, semi-statically through RRC signaling, k (k<=N) aggregationlevels in the N aggregation levels as aggregation levels that can besupported by the control channel to be transmitted.

A form of semi-static configuration through RRC signaling is a bitmap.

If the number of aggregation levels of the control channel to betransmitted is N, the numbers of control channel candidatescorresponding to any p (p<=4) aggregation levels in 4 aggregation levels(1, 2, 4, 8) in an original protocol are respectively configured forcorresponding aggregation levels in the N aggregation levels of thecontrol channel to be transmitted, and the numbers of control channelcandidates corresponding to remaining (4-p) aggregation levels in the 4aggregation levels (1, 2, 4, 8) in the original protocol arecorrespondingly configured for remaining N-p aggregation levels in the Naggregation levels of the control channel to be transmitted.

Optionally, the apparatus includes a detecting unit. When theaggregation levels supported by the control channel to be transmittedinclude 32, and the number of available resource elements in eachphysical resource block pair except resource elements of other signals,such as a CRS, a DMRS, a CSI-RS, a PDCCH, is greater than or equal to72, the detecting unit does not detect control channel candidates ataggregation level 32; otherwise, the detecting unit detects the controlchannel candidates at aggregation level 32; or, when the aggregationlevels supported by the control channel to be transmitted do not include32, and the number of available resource elements in each physicalresource block pair except resource elements of other signals, such as aCRS, a DMRS, a CSI-RS, a PDCCH, is less than 72, the detecting unitdetects control channel candidates at aggregation level 8.

When the control channel to be transmitted is transmitted with anextended cyclic prefix, and the supported aggregation levels include 16,and the number of available resource elements in each physical resourceblock pair except resource elements of other signals, such as a CRS, aDMRS, a CSI-RS, a PDCCH, is greater than or equal to 72, the detectingunit does not detect control channel candidates at aggregation level 16;otherwise, the detecting unit detects the control channel candidates ataggregation level 16; or, when the control channel to be transmitted istransmitted with an extended cyclic prefix, and the supportedaggregation levels do not include 16, and the number of availableresource elements in each physical resource block pair except resourceelements of other signals, such as a CRS, a DMRS, a CSI-RS, a PDCCH, isless than 72, the detecting unit detects PDCCH candidates at aggregationlevel 8.

The K_(L) and K_(D) for transmitting the control channel are configured,and the number of physical resource block pairs included in each set isconfigured; or the K_(L) and K_(D) for transmitting the control channelare fixed, the number of physical resource block pairs included in eachset is configured, and allocation of all control channel candidates ateach aggregation level to the K_(L) and K_(D) sets is fixed.

Herein the configuration refers to parameters configured by the basestation for the UE through higher-layer signaling, which means, valuesof the K_(L) and K_(D) and the number of physical resource block pairsincluded in each set may all be configured by the base station for theUE.

In the method and apparatus for allocating control channel candidatesaccording to the embodiments of the present application, K sets fortransmitting a control channel are determined, and control channelcandidates at each aggregation level are allocated to at least one setin the K sets according to at least one of aggregation levels supportedby the control channel to be transmitted, the number of control channelcandidates corresponding to each aggregation level, the K sets fortransmitting the control channel, and types of the sets. Therefore,control channel candidates at different aggregation levels can beallocated to K ePDCCH sets, and a search space of a UE is defined,thereby reducing complexity of blind detection performed by the UE.

The foregoing descriptions are merely specific embodiments of thepresent application, but are not intended to limit the protection scopeof the present application. Any variation or replacement readily figuredout by a person skilled in the art within the technical scope disclosedin the present application shall fall within the protection scope of thepresent application. Therefore, the protection scope of the presentapplication shall be subject to the protection scope of the claims.

What is claimed is:
 1. A method for detecting a control channel, themethod comprising: obtaining, by user equipment (UE), K sets configuredfor transmitting a control channel, wherein each of the K sets comprisesat least one physical resource block pair, and K is an integer greaterthan 0; detecting, by the UE, control channel candidates on at least oneset of the K sets according to aggregation levels supported by thecontrol channel, quantities of control channel candidates of theaggregation levels, the K sets configured for transmitting the controlchannel, and types of the K sets; wherein the types of the K setscomprise one or both of a localized transmission mode and a distributedtransmission mode, and a quantity of sets of the localized transmissionmode is K_(L), and a quantity of sets of the distributed transmissionmode is K_(D), K_(L)+K_(D)=K, wherein K_(L) and K_(D) are integersgreater than or equal to 0; and the aggregation levels supported by thecontrol channel comprise one or more of the following levels: anaggregation level supported by the localized transmission mode, anaggregation level supported by the distributed transmission mode, and anaggregation level supported by both the localized transmission mode andthe distributed transmission mode.
 2. The method according to claim 1,wherein the UE detects the control channel candidates according to thefollowing control channel candidate allocation: when K_(L) is a positiveinteger and K_(D)=0, all control channel candidates at the aggregationlevel supported by the localized transmission mode are allocated to atleast one of the K_(L) sets; or when K_(D) is a positive integer andK_(L)=0, all control channel candidates at the aggregation levelsupported by the distributed transmission mode are allocated to at leastone of the K_(D) sets; or when both K_(L) and K_(D) are positiveintegers, all control channel candidates at the aggregation levelsupported by both the localized transmission mode and the distributedtransmission mode are allocated to at least one of the K_(L) sets and atleast one of the K_(D) sets.
 3. The method according to claim 2, whereinthe aggregation level supported by both the localized transmission modeand the distributed transmission mode comprises a first aggregationlevel and a second aggregation level, and wherein: at least one half ofall control channel candidates at the first aggregation level supportedby both the localized transmission mode and the distributed transmissionmode are allocated to at least one of the K_(L) sets; and at least onehalf of all control channel candidates at the second aggregation levelsupported by both the localized transmission mode and the distributedtransmission mode are allocated to at least one of the K_(D) sets. 4.The method according to claim 3, wherein when the aggregation levelsupported by both the localized transmission mode and the distributedtransmission mode comprises aggregation level 1, aggregation level 2,aggregation level 4, and aggregation level 8, the first aggregationlevel comprises aggregation level 1 and aggregation level 2, and thesecond aggregation level comprises aggregation level 4 and aggregationlevel
 8. 5. The method according to claim 3, wherein when theaggregation level supported by both the localized transmission mode andthe distributed transmission mode comprises aggregation level 2,aggregation level 4, aggregation level 8, and aggregation level 16, thefirst aggregation level comprises aggregation level 2 and aggregationlevel 4, and the second aggregation level comprises aggregation level 8and aggregation level
 16. 6. The method according to claim 2, whereinwhen both K_(L) and K_(D) are positive integers, all control channelcandidates at the aggregation level supported by both the localizedtransmission mode and the distributed transmission mode are allocated toat least one of the K_(L) sets and at least one of the K_(D) sets,wherein: quantities of control channel candidates allocated to the K_(L)sets and the K_(D) sets are determined according to a ratio betweenquantities of sets used for the aggregation level in the K_(D) sets andthe K_(L) sets; or quantities of control channel candidates allocated tothe K_(L) sets and the K_(D) sets are determined according to a ratiobetween total quantities of physical resource blocks in sets used forthe aggregation level in the K_(D) sets and the K_(L) sets; or aquantity of control channel candidates allocated to each of the K_(L)sets and the K_(D) sets is determined according to a ratio of a quantityof physical resource blocks of each set in sets used for the aggregationlevel in the K_(D) sets and the K_(L) sets.
 7. The method according toclaim 2, wherein when K_(L) is a positive integer and K_(D)=0, or K_(D)is a positive integer and K_(L)=0: a quantity of control channelcandidates allocated to each set in the K_(D) sets or K sets isdetermined according to a quantity of sets used for the aggregationlevel in K_(D) or K_(L) sets; or a quantity of control channelcandidates allocated to each set in the K_(D) sets or K_(L) sets isdetermined according to a ratio of a quantity of physical resourceblocks of each set in sets used for the aggregation level in K_(D) orK_(L) sets.
 8. The method according to claim 2, wherein: at anaggregation level, when a quantity of control channel candidatesconfigured for the K_(L) sets is greater than 1, a quantity of controlchannel candidates in each set is determined according to a quantity ofphysical resource blocks comprised in each set that can support theaggregation level in the K_(L) sets or a quantity of sets that cansupport the aggregation level in the K_(L) sets, wherein K_(L) isgreater than 1; or at an aggregation level, when a quantity of controlchannel candidates configured for the K_(D) sets is greater than 1, aquantity of control channel candidates in each set is determinedaccording to a quantity of physical resource blocks comprised in eachset that can support the aggregation level in the K_(D) sets or aquantity of sets that can support the aggregation level in the K_(D)sets, wherein K_(D) is greater than
 1. 9. An apparatus for detecting acontrol channel, the apparatus comprising: a processor; and anon-transitory computer readable storage medium, wherein thenon-transitory computer readable storage medium stores a program that,when executed by the processor, causes the apparatus to: obtain K setsconfigured for transmitting a control channel, wherein each of the Ksets comprises at least one physical resource block pair, and K is aninteger greater than 0, and detect control channel candidates on atleast one set of the K sets according to aggregation levels supported bythe control channel, quantities of control channel candidates of theaggregation levels, the K sets configured for transmitting the controlchannel, and types of the K sets; wherein the types of the K setscomprise one or both of a localized transmission mode and a distributedtransmission mode, and a quantity of sets of the localized transmissionmode is K_(L), and a quantity of sets of the distributed transmissionmode is K_(D), K_(L)+K_(D)=K, wherein K_(L) and K_(D) are integersgreater than or equal to 0; and the aggregation levels supported by thecontrol channel comprise one or more of the following levels: anaggregation level supported by the localized transmission mode, anaggregation level supported by the distributed transmission mode, and anaggregation level supported by both the localized transmission mode andthe distributed transmission mode.
 10. The apparatus according to claim9, wherein the control channel candidates are detected according to thefollowing control channel candidate allocation: when K_(L) is a positiveinteger and K_(D)=0, all control channel candidates at the aggregationlevel supported by the localized transmission mode are allocated to atleast one of the K_(L) sets; or when K_(D) is a positive integer andK_(L)=0, all control channel candidates at the aggregation levelsupported by the distributed transmission mode are allocated to at leastone of the K_(D) sets; or when both K_(L) and K_(D) are positiveintegers, all control channel candidates at the aggregation levelsupported by both the localized transmission mode and the distributedtransmission mode are allocated to at least one of the K_(L) sets and atleast one of the K_(D) sets.
 11. The apparatus according to claim 10,wherein the aggregation level supported by both the localizedtransmission mode and the distributed transmission mode comprises afirst aggregation level and a second aggregation level, and wherein: atleast one half of all control channel candidates at the firstaggregation level supported by both the localized transmission mode andthe distributed transmission mode are allocated to at least one of theK_(L) sets; and at least one half of all control channel candidates atthe second aggregation level supported by both the localizedtransmission mode and the distributed transmission mode are allocated toat least one of the K_(D) sets.
 12. The apparatus according to claim 11,wherein when the aggregation level supported by both the localizedtransmission mode and the distributed transmission mode comprisesaggregation level 1, aggregation level 2, aggregation level 4, andaggregation level 8, the first aggregation level comprises aggregationlevel 1 and aggregation level 2, and the second aggregation levelcomprises aggregation level 4 and aggregation level
 8. 13. The apparatusaccording to claim 11, wherein when the aggregation level supported byboth the localized transmission mode and the distributed transmissionmode comprises aggregation level 2, aggregation level 4, aggregationlevel 8, and aggregation level 16, the first aggregation level comprisesaggregation level 2 and aggregation level 4, and the second aggregationlevel comprises aggregation level 8 and aggregation level
 16. 14. Theapparatus according to claim 10, wherein when both K_(L) and K_(D) arepositive integers, all control channel candidates at the aggregationlevel supported by both the localized transmission mode and thedistributed transmission mode are allocated to at least one of the K_(L)sets and at least one of the K_(D) sets, wherein quantities of controlchannel candidates allocated to the K_(L) sets and the K_(D) sets aredetermined according to a ratio between quantities of sets used for theaggregation level in the K_(D) sets and the K_(L) sets; or quantities ofcontrol channel candidates allocated to the K_(L) sets and the K_(D)sets are determined according to a ratio between total quantities ofphysical resource blocks in sets used for the aggregation level in theK_(D) sets and the K_(L) sets; or a quantity of control channelcandidates allocated to each of the K_(L) sets and the K_(D) sets isdetermined according to a ratio of a quantity of physical resourceblocks of each set in sets used for the aggregation level in the K_(D)sets and the K_(L) sets.
 15. The apparatus according to claim 10,wherein when K_(L) is a positive integer and K_(D)=0, or K_(D) is apositive integer and K_(L)=0: a quantity of control channel candidatesallocated to each set in the K_(D) sets or K_(L) sets is determinedaccording to a quantity of sets used for the aggregation level in K_(D)or K_(L) sets; or a quantity of control channel candidates allocated toeach set in the K_(D) sets or K_(L) sets is determined according to aratio of a quantity of physical resource blocks of each set in sets usedfor the aggregation level in K_(D) or K_(L) sets.
 16. The apparatusaccording to claim 10, wherein: at an aggregation level, when a quantityof control channel candidates configured for the K_(L) sets is greaterthan 1, a quantity of control channel candidates in each set isdetermined according to a quantity of physical resource blocks comprisedin each set that can support the aggregation level in the K_(L) sets ora quantity of sets that can support the aggregation level in the K_(L)sets, wherein K_(L) is greater than 1; or at an aggregation level, whena quantity of control channel candidates configured for the K_(D) setsis greater than 1, a quantity of control channel candidates in each setis determined according to a quantity of physical resource blockscomprised in each set that can support the aggregation level in theK_(D) sets or a quantity of sets that can support the aggregation levelin the K_(D) sets, wherein K_(D) is greater than
 1. 17. A non-transitorycomputer readable storage medium comprising instructions that, whenexecuted by a processor, cause the processor to: obtain K setsconfigured for transmitting a control channel, wherein each of the Ksets comprises at least one physical resource block pair, and K is aninteger greater than 0; detect control channel candidates on at leastone set of the K sets according to aggregation levels supported by thecontrol channel, quantities of control channel candidates of theaggregation levels, the K sets configured for transmitting the controlchannel, and types of the K sets; wherein the types of the K setscomprise one or both of a localized transmission mode and a distributedtransmission mode, and a quantity of sets of the localized transmissionmode is K_(L), and a quantity of sets of the distributed transmissionmode is K_(D), K_(L)K_(D)=K, wherein K_(L) and K_(D) are integersgreater than or equal to 0; and the aggregation levels supported by thecontrol channel comprise one or more of the following levels: anaggregation level supported by the localized transmission mode, anaggregation level supported by the distributed transmission mode, and anaggregation level supported by both the localized transmission mode andthe distributed transmission mode.
 18. The non-transitory computerreadable storage medium according to claim 17, wherein execution of theinstructions further causes the processor to detect the control channelcandidates according to the following control channel candidateallocation: when K_(L) is a positive integer and K_(D)=0, all controlchannel candidates at the aggregation level supported by the localizedtransmission mode are allocated to at least one of the K_(L) sets; orwhen K_(D) is a positive integer and K_(L)=0, all control channelcandidates at the aggregation level supported by the distributedtransmission mode are allocated to at least one of the K_(D) sets; orwhen both K_(L) and K_(D) are positive integers, all control channelcandidates at the aggregation level supported by both the localizedtransmission mode and the distributed transmission mode are allocated toat least one of the K_(L) sets and at least one of the K_(D) sets.